http://bugs.winehq.org/show_bug.cgi?id=21070
--- Comment #1 from Roderick Colenbrander thunderbird2k@gmail.com 2009-12-19 05:16:56 --- That patch in combination with previous patches moves 2D rendering over to XRender. This is needed to fix some major 2D rendering issues and in general it also improves performance a lot. I'm not sure what display drivers you are using but I fear that they don't accelerate some parts of XRender which results in software rendering. What happens if you don't use compiz?