Comment 60 for bug 220628

This appears to be a problem with a known fix.

Symptoms: firefox and other programs crash with BadIdChoice errors.
https://bugzilla.mozilla.org/show_bug.cgi?id=458092
https://bugzilla.redhat.com/show_bug.cgi?id=458657
https://bugs.launchpad.net/ubuntu/+source/firefox-3.0/+bug/220628
https://bugs.launchpad.net/firefox/+bug/255195

It looks as if this has been tracked down.
Start of thread: http://lists.freedesktop.org/archives/xcb/2009-January/004247.html
Note that this thread crosses a month boundary so that threading in the archive doesn't get you to postings in February.
Continue here: http://lists.freedesktop.org/archives/xcb/2009-February/004287.html

The latest proposed patch is attached to this: http://lists.freedesktop.org/archives/xcb/2009-February/004326.html
except that I don't see the attachment. Perhaps scrubbed by the archiver.
This version seems to have it:
http://article.gmane.org/gmane.comp.freedesktop.xcb/4192
Subsequent messages suggest that a little polishing is still going on.