http://bugs.winehq.org/show_bug.cgi?id=27998
--- Comment #3 from A Wine user RandomAccountName@mail.com 2011-08-15 06:04:51 CDT --- I see this bug, too.
(In reply to comment #2)
You might want to give this patch a go first, before running a starting a bisect session:
That patch alone didn't help, but combining it with http://bugs.winehq.org/attachment.cgi?id=35881 made the tab bar and GIFs render as expected.