<?php
header( 'Content-Type: text/xml; charset=UTF-8' );
echo '<' . '?xml version="1.0" encoding="UTF-8"?' . '>' . "\n";
bb_generator( 'comment' );

function datefix($buffer) {
	/*
	 * fix della data in modo da tenerla in inglese, rispettando
	 * le specifiche dei feed RSS
	 */
	 return gmdate('D, d M Y H:i:s +0000', $buffer);
}

function callback($buffer)
{
	/*
	 * sistema il codice rimuovendo la doppia codifica di "&" e
	 * rimuove il carattere "&nbsp;" che crea problemi con UTF-8
	 * in questo modo ho il testo del post dopo che i plugin (tipo
	 * le faccine) hanno applicato le loro modifiche html e ritorno
	 * il codice html senza entities ma in forma pura
	 */

	$single = str_replace("&", "&", $buffer);
	$spaced = str_replace("&nbsp;", " ", $single);
	return html_entity_decode($spaced);
}

?>
<rss version="2.0"
	xmlns:content="http://purl.org/rss/1.0/modules/content/"
	xmlns:dc="http://purl.org/dc/elements/1.1/"
	xmlns:atom="http://www.w3.org/2005/Atom">
	<channel>
		<title><?php echo $title; ?></title>
		<link><?php echo $link; ?></link>
		<description><![CDATA[<?php echo $description; ?>]]></description>
		<language><?php esc_html( bb_option('language') ); ?></language>
		<pubDate><?php echo gmdate('D, d M Y H:i:s +0000'); ?></pubDate>
		<?php bb_generator( 'rss2' ); ?>
		<textInput>
			<title><![CDATA[<?php _e('Search'); ?>]]></title>
			<description><![CDATA[<?php _e('Search all topics from these forums.'); ?>]]></description>
			<name>q</name>
			<link><?php bb_uri('search.php'); ?></link>
		</textInput>
		<atom:link href="<?php echo $link_self; ?>" rel="self" type="application/rss+xml" />

<?php foreach ($posts as $bb_post) : ?>
		<item>
			<title><?php post_author(); ?> <?php _e('on')?> "<?php topic_title( $bb_post->topic_id ); ?>"</title>
			<link><?php post_link(); ?></link>
			<pubDate><?php 

			ob_start("datefix");
			bb_post_time('U');
			ob_end_flush();

			?></pubDate>
			<dc:creator><?php post_author(); ?></dc:creator>
			<guid isPermaLink="false"><?php post_id(); ?>@<?php bb_uri(); ?></guid>
			<description><![CDATA[<?php

			ob_start("callback");
			post_text();
			ob_end_flush();

			?>]]></description>
		</item>
<?php endforeach; ?>

	</channel>
</rss>

Sorry for comments in italian.
BTW @ yoyopop, I don't remember in which topic, but I read on this forum that the problem is related to some plugins having extra spaces in their code before the opening "<?php" tag. Check it...

Thanks,
Pagal

Ho provato a fare tutte le modifiche possibile, ma non ho trovato soluzione... come risolvo? Ho anche sostituito i file rss2.php, rss.php con quelli di default (anche se prima non li avevo toccati) ma nulla

Errore interpretazione XML: la dichiarazione XML o testuale non è all'inizio di un'entità
Indirizzo: http://ciobomario.com/forum/rss/forum/presentati
Linea numero 2, colonna 1:<?xml version="1.0" encoding="UTF-8"?>
^

This problem happens when using the default theme.

Any ideas? kirpi.it didn't say how it was fixed!?

I removed all "»" in the rss.php

Replace the code of your rss.php with the following code and it should work:

<?php<br />
require('./bb-load.php');</p>
<p>// Determine the type of feed and the id of the object<br />
if ( isset($_GET['view']) || bb_get_path() == 'view' ) {</p>
<p>	// View<br />
	$feed = 'view';<br />
	$feed_id = isset($_GET['view']) ? $_GET['view'] : bb_get_path(2);</p>
<p>} elseif ( isset($_GET['topic']) || bb_get_path() == 'topic' ) {</p>
<p>	// Topic<br />
	$feed = 'topic';<br />
	$topic = get_topic(isset($_GET['topic']) ? $_GET['topic'] : bb_get_path(2));<br />
	$feed_id = $topic->topic_id;</p>
<p>} elseif ( isset($_GET['profile']) || bb_get_path() == 'profile' ) {</p>
<p>	// Profile<br />
	$feed = 'profile';<br />
	$feed_id = isset($_GET['profile']) ? $_GET['profile'] : bb_get_path(2);</p>
<p>} elseif ( isset($_GET['tag']) || bb_get_path() == 'tags' ) {</p>
<p>	if ( isset($_GET['topics']) || bb_get_path(3) == 'topics' ) {<br />
		// Tag recent topics<br />
		$feed = 'tag-topics';<br />
	} else {<br />
		// Tag recent posts<br />
		$feed = 'tag-posts';<br />
	}<br />
	$feed_id = isset($_GET['tag']) ? $_GET['tag'] : bb_get_path(2);</p>
<p>} elseif ( isset($_GET['forum']) || bb_get_path() == 'forum' ) {</p>
<p>	if ( isset($_GET['topics']) || bb_get_path(3) == 'topics' ) {<br />
		// Forum recent topics<br />
		$feed = 'forum-topics';<br />
	} else {<br />
		// Forum recent posts<br />
		$feed = 'forum-posts';<br />
	}<br />
	$forum = bb_get_forum(isset($_GET['forum']) ? $_GET['forum'] : bb_get_path(2));<br />
	$feed_id = $forum->forum_id;</p>
<p>} elseif ( isset($_GET['topics']) || bb_get_path() == 'topics' ) {</p>
<p>	// Recent topics<br />
	$feed = 'all-topics';</p>
<p>} else {</p>
<p>	// Recent posts<br />
	$feed = 'all-posts';</p>
<p>}</p>
<p>// Initialise the override variable<br />
$bb_db_override = false;<br />
do_action( 'bb_rss.php_pre_db' );</p>
<p>if ( !$bb_db_override ) {</p>
<p>	// Get the posts and the title for the given feed<br />
	switch ($feed) {<br />
		case 'view':<br />
			if ( !isset($bb_views[$feed_id]) )<br />
				die();<br />
			if ( !$bb_views[$feed_id]['feed'] )<br />
				die();<br />
			if ( !$topics_object = new BB_Query( 'topic', $bb_views[$feed_id]['query'], "bb_view_$feed_id" ) )<br />
				die();</p>
<p>			$topics = $topics_object->results;<br />
			if ( !$topics || !is_array($topics) )<br />
				die();</p>
<p>			$posts = array();<br />
			foreach ($topics as $topic) {<br />
				$posts[] = bb_get_first_post($topic->topic_id);<br />
			}</p>
<p>			$title = esc_html( sprintf( __( '%1$s View: %2$s' ), bb_get_option( 'name' ), $bb_views[$feed_id]['title'] ) );<br />
			$link = get_view_link($feed_id);<br />
			$link_self = bb_get_view_rss_link($feed_id);<br />
			break;</p>
<p>		case 'topic':<br />
			if ( !$topic = get_topic ( $feed_id ) )<br />
				die();<br />
			if ( !$posts = get_thread( $feed_id, 0, 1 ) )<br />
				die();<br />
			$title = esc_html( sprintf( __( '%1$s  Topic: %2$s' ), bb_get_option( 'name' ), get_topic_title() ) );<br />
			$link = get_topic_link($feed_id);<br />
			$link_self = get_topic_rss_link($feed_id);<br />
			break;</p>
<p>		case 'profile':<br />
			if ( bb_get_option( 'mod_rewrite' ) === 'slugs' ) {<br />
				$user = bb_get_user_by_nicename( $feed_id );<br />
			} else {<br />
				$user = bb_get_user( $feed_id );<br />
			}<br />
			if ( !$user ) {<br />
				die();<br />
			}<br />
			if ( !$posts = get_user_favorites( $user->ID ) ) {<br />
				die();<br />
			}<br />
			$title = esc_html( sprintf( __( '%1$s  User Favorites: %2$s' ), bb_get_option( 'name' ), $user->user_login ) );<br />
			$link = bb_get_profile_link($feed_id);<br />
			$link_self = get_favorites_rss_link($feed_id);<br />
			break;</p>
<p>		case 'tag-topics':<br />
			if ( !$tag = bb_get_tag( $feed_id ) )<br />
				die();<br />
			if ( !$topics = get_tagged_topics( array( 'tag_id' => $tag->tag_id, 'page' => 0 ) ) )<br />
				die();</p>
<p>			$posts = array();<br />
			foreach ($topics as $topic) {<br />
				$posts[] = bb_get_first_post($topic->topic_id);<br />
			}</p>
<p>			$title = esc_html( sprintf( __( '%1$s  Tag: %2$s - Recent Topics' ), bb_get_option( 'name' ), bb_get_tag_name() ) );<br />
			$link = bb_get_tag_link($feed_id);<br />
			$link_self = bb_get_tag_topics_rss_link($feed_id);<br />
			break;</p>
<p>		case 'tag-posts':<br />
			if ( !$tag = bb_get_tag( $feed_id ) )<br />
				die();<br />
			if ( !$posts = get_tagged_topic_posts( array( 'tag_id' => $tag->tag_id, 'page' => 0 ) ) )<br />
				die();<br />
			$title = esc_html( sprintf( __( '%1$s  Tag: %2$s - Recent Posts' ), bb_get_option( 'name' ), bb_get_tag_name() ) );<br />
			$link = bb_get_tag_link($feed_id);<br />
			$link_self = bb_get_tag_posts_rss_link($feed_id);<br />
			break;</p>
<p>		case 'forum-topics':<br />
			if ( !$topics = get_latest_topics( $feed_id ) )<br />
				die();</p>
<p>			$posts = array();<br />
			foreach ($topics as $topic) {<br />
				$posts[] = bb_get_first_post($topic->topic_id);<br />
			}</p>
<p>			$title = esc_html( sprintf( __( '%1$s  Forum: %2$s - Recent Topics' ), bb_get_option( 'name' ), get_forum_name( $feed_id ) ) );<br />
			$link = get_forum_link($feed_id);<br />
			$link_self = bb_get_forum_topics_rss_link($feed_id);<br />
			break;</p>
<p>		case 'forum-posts':<br />
			if ( !$posts = bb_get_latest_forum_posts( $feed_id ) )<br />
				die();<br />
			$title = esc_html( sprintf( __( '%1$s  Forum: %2$s - Recent Posts' ), bb_get_option( 'name' ), get_forum_name( $feed_id ) ) );<br />
			$link = get_forum_link($feed_id);<br />
			$link_self = bb_get_forum_posts_rss_link($feed_id);<br />
			break;</p>
<p>		// Get just the first post from the latest topics<br />
		case 'all-topics':<br />
			if ( !$topics = get_latest_topics() )<br />
				die();</p>
<p>			$posts = array();<br />
			foreach ($topics as $topic) {<br />
				$posts[] = bb_get_first_post($topic->topic_id);<br />
			}</p>
<p>			$title = esc_html( sprintf( __( '%1$s  Recent Topics' ), bb_get_option( 'name' ) ) );<br />
			$link = bb_get_uri();<br />
			$link_self = bb_get_topics_rss_link();<br />
			break;</p>
<p>		// Get latest posts by default<br />
		case 'all-posts':<br />
		default:<br />
			if ( !$posts = bb_get_latest_posts( 35 ) )<br />
				die();<br />
			$title = esc_html( sprintf( __( '%1$s  Recent Posts' ), bb_get_option( 'name' ) ) );<br />
			$link = bb_get_uri();<br />
			$link_self = bb_get_posts_rss_link();<br />
			break;<br />
	}<br />
}</p>
<p>bb_send_304( $posts[0]->post_time );</p>
<p>if (!$description = esc_html( bb_get_option('description') )) {<br />
	$description = $title;<br />
}<br />
$title = apply_filters( 'bb_title_rss', $title, $feed );<br />
$description = apply_filters( 'bb_description_rss', $description, $feed );<br />
$posts = apply_filters( 'bb_posts_rss', $posts, $feed );<br />
$link_self = apply_filters( 'bb_link_self_rss', $link_self, $feed );</p>
<p>bb_load_template( 'rss2.php', array('bb_db_override', 'title', 'description', 'link', 'link_self'), $feed );</p>
<p>?>

My experience was the same when applying the patch, but then I wondered how soon I should have seen the results.

I applied the patches suggested via the trac and your comments but my rss feed is still returning invalid in Chrome, Opera and Firefox (in Safari it works fine)

it does seem to be something wrong with the markup via an extra space in front of the xml declaration somewhere...

Anyone have any ideas??

Chrome:

error on line 1 at column 6: XML declaration allowed only at the start of the document

Opera:

XML parsing failed: syntax error (Line: 1, Character: 1)

Error:XML declaration not at beginning of document

and it shows a space in front of the initial <? xml

Firefox:

XML Parsing Error: XML or text declaration not at start of entity
Location: /rss.php?topic=2074
Line Number 1, Column 2: <?xml version="1.0" encoding="UTF-8"?>
-^

http://bbpress.org/forums/topic/are-usernames-with-spaces-sensible

@bbback: you can avoid echoing get_ functions by dropping the get_, there's always an echo alias function

@kirpi.it: my bad, I left it using an echo function rather than returning the output

<a href="<?php echo esc_attr( get_user_profile_link( get_post_author_id() ) ); ?>"><?php echo get_post_author(); ?></a>

<?php bb_get_profile_link(post_author()); ?>
just renders the poster name, without any link.

<a href="http://www.example.com/forum/profile/<?php bb_get_profile_link(post_author()); ?>">
<?php bb_get_profile_link(post_author()); ?>
</a>

Hardcoding the path is not nice, but at least it works.

:-)
Thank you!

Would it really be that hard to get the poster name and link it to his/her profile page, quite simply?
I cannot find how.

<p class="login">
	<?php printf(__('Welcome, %1$s'), bb_get_profile_link(bb_get_current_user_info( 'name' )));?>
	<?php bb_admin_link( 'before= | ' );?>
	| <?php bb_logout_link(); ?>
</p>

So you'd want bb_get_profile_link(bb_get_current_user_info( 'name' ))

Link should most probably look like
http://www.example.com/forum/profile/user

The right code is probably hidden in the header, where it says

Welcome, User | Log Out

That User link is the one I'm after, but cannot find out how it is built.