Sorry, I forgot I was talking about tags.php specifically. Here’s a tags URL.
is what’s in the sitemap.
curl -I "http://www.riversideinfo.org/forum/tags.php?tag%3Dtif"
returns a 302 header.
If you unencode it, and then curl -I:
curl -I "http://www.riversideinfo.org/forum/tags.php?tag=tif"
returns a 200 header.
Maybe it’s just the urlencoding of the = that causes it to redirect? That’s the only difference between the two URLs here.