http://bugs.winehq.org/show_bug.cgi?id=21043
--- Comment #12 from Roderick Colenbrander thunderbird2k@gmail.com 2009-12-21 09:58:41 --- What happens if you set ClientSideWithRender to N (see http://wiki.winehq.org/UsefulRegistryKeys). If that fixes the performance drop then bug 21070 is a duplicate of this one.