There are problems when building the musicbrainz_collate extension in Ubuntu 11.10, as noted by various people at:
http://chatlogs.musicbrainz.org/musicbrainz-devel/2011/2011-11/2011-11-22.html#T14-50-42-4606
http://chatlogs.musicbrainz.org/musicbrainz-devel/2011/2011-10/2011-10-17.html#T09-16-44-373845
http://forums.musicbrainz.org/viewtopic.php?id=3277
and now me: http://chatlogs.musicbrainz.org/musicbrainz-devel/2012/2012-01/2012-01-03.html#T00-22-35-725683

Since Ubuntu is our recommended distro, I think we should make a note in the INSTALL file that people using 11.10 need to compile the extension with gcc-4.4 and what steps they need to do in order to do that.