As I've seen on IRC, Firefox 18 has the some problem as Chromium had [1]. It seems to require jpeg-turbo [2] which may be the reason.
So, if you update to Firefox 18, which is currently in the testing repository: $ querypkg firefox --repo limbo >> @@ Please wait, downloading data... >> @@ Package: www-client/firefox-18.0 >> Arch: amd64 >> Revision: 0 >> Slot: 0 >> Size: 28.9MB >> Downloads: 105624 >> Vote: 3.7333 >> spm_repo: sabayon-distro >> Homepage: http://www.mozilla.com/firefox >> Description: Firefox Web Browser >> Date: 2013-01-11 11:30:59.900000 >> License: GPL-2 LGPL-2.1 MPL-2.0 >> Last change: N/A >> Keyword: firefox and encounter problems with JPEG images, make sure you don't have media-libs/jpeg-8* installed. Reinstalling media-libs/libjpeg-turbo may remove it automatically; if not, uninstall jpeg-8* by hand and pay attention not to remove the whole system because of reverse dependencies (--nodeps may be handy) - and if you see applications stop working because they can't find libjpeg, reinstall jpeg-turbo. (So much fuss shouldn't be needed, but I want to cover possible problem cases.) Enjoy! [1] http://bugs.sabayon.org/show_bug.cgi?id=3791 [2] https://bugs.gentoo.org/show_bug.cgi?id=451180
