The bug is described in GNOME bugzilla 152175. The patch is only available in GNOME 2.9.X right now. The bug is fixed in upstream 2.8 branch in CVS, but no release are available yet. The lack of this patch can cause breakage with a lot of applications where the default value can't be grabbed correctly. (The bug is also present on RHEL4).
This bug has caused bugs to appear in Totem (black screen on first start), and the "Default Applications" capplet where http wouldn't be enabled by default.
Was fixed in FC4.