In a world update today, portage downgraded xulrunner from 1.9.1.4 to 1.9.1.3-r1. This is wrong since I'm using Firefox 3.5.4. xulrunner 1.9.1.3 is for Firefox 3.5.3, not 3.5.4.
That's right, something went wrong: in the just-updated mozilla-firefox-3.5.4.ebuild XUL_PV is marked 1.9.1.3, it should be XUL_PV="1.9.1.4"
I just ran into this now after syncing and doing a world update, and there are other packages that require xulrunner 1.9.1.4. I could add this to my own overlay to fix it, but I think I'll just remove firefox for now and start updating.
This has been fixed in CVS: 30 Oct 2009; Tristan Heaven <nyhm@gentoo.org> mozilla-firefox-3.5.4.ebuild: Depend on xulrunner-1.9.1.4, not 1.9.1.3 (shoot me if I'm wrong) thanks for reporting