For those people with an early-2009 Mac Pro (Nehalem) with an ATI 4800 graphic card, here are more detailed instructions for CrossOver Games (Version 8) -- you will need to modify the file user.reg located at
~/Users/[HOME]/Library/Application Support/CrossOver Games/Bottles/winxp/user.reg
Within user.reg, there will need to be two lines in the following order:
[Software\Wine\Direct3D] 1254687807
"UseGLSL"="disabled"
Disabling UseGLSL is what makes the tree issue go away, but there is still no red bar for vitality (upper left-hand corner of screen), which is critical for playing an advanced game, since you need to rest or drink magic prior to running out of vitality (or else you die). There is a visible line drawn on the right hand of Geralt the Witcher (like a marionette), but the vitality red bar is the most important problem I see at this point. In the advanced game options inside the Witcher game, I had to turn down "Anisotropic Filtering" to "1X" to avoid the game crashing, but everything else can be turned up to the maximum (e.g., super detailed maxed out is okay) -- out of the box, the antialiasing option is disabled. This took me many hours to figure out, so I hope this forum entry saves everyone else a lot of time (and that it attracts someone smarter than me). Please post a solution for the red vitality bar if one is found.