OK, if you change line 189 of forum/bb-includes/backpress/class.wp-auth.php to this:
$key = wp_hash( $username . $pass_frag . ‘|’ . $expiration, $scheme );
It works.
The standard is this:
$key = call_user_func(backpress_get_option(‘hash_function_name’), $username . $pass_frag . ‘|’ . $expiration, $scheme );
Which doesn’t work. Has the algorithm changed in the latest version of WordPress?