http://bugs.winehq.org/show_bug.cgi?id=24877
--- Comment #11 from Solitary t.hlavnicka@centrum.cz 2010-12-30 17:54:09 CST --- Ok, I just figured out a small workaround... playing in windowed mode (and I mean Baldur's Gate, not Wine). Pressing ALT+ENTER makes Baldur's Gate switch into windowed mode and rendering is suddenly correct and game playable (no slugging).
Hope it helps and Happy New Year!