http://bugs.winehq.org/show_bug.cgi?id=24877
--- Comment #10 from Solitary t.hlavnicka@centrum.cz 2010-12-30 17:18:11 CST --- I just discovered interesting thing during my tryings with workarounds.
I started Wine in windowed mode (it's essential) and started playing BG1 in this mode (it's still badly rendered, of course). But when I pressed ALT+F4 I got dialog window with question if I want to close the game or not. When I pressed 'No' it didn't return into previous state, but it ended up in total black screen instead, with game still running (sound is playing). On the other hand, if I pressed 'Yes', game became fully playable (rendering is correct and game is fluent again - both ingame and menu). Too bad it's like that only for ~2seconds, due to 'Yes' on ALT+F4 question. (there is no ~2seconds delay in Wine fullscreen mode, so as I said, windowed mode is essential)
Therefore I think it's just some glitch more then HW or drivers problem, otherwise it wouldn't be able to render the game correctly at all.
Wine started throwing different output during that playable moment (only when mouse was moving), instead of "WINED3DFMT_B5G6R5_UNORM." (which is thrown all the time)
---- fixme:d3d_surface:surface_download_data Readback conversion not supported for format WINED3DFMT_B8G8R8X8_UNORM. ----
I hope this can help to come up with some fix or workaround.