It's hard for me to describe, see the attached video.
The bug is definetely somewhere in MESA, since the game runs fine with the same Wine's version with nVidia card and when I've tried to run it in VMWare (3D support via WDDM driver) I've got the same result.
http://www.gamefront.com/files/11799044/Kings-Bounty-The-Legend-Demo/ - game demo.
Oops. Attachment is too large. Video is here: http://videobin.org/+611/6o0.html
Ouch, that's bad. We don't tend to work on issues with wine apps much, since it's a really painful environment to work in. An apitrace (minimal as possible) of the app failing might be a way to bump the priority for us :)