In the configuration program try checking the 'Use AlphaBit' option, or switch to Software rather than Direct3D.
For the Steam version you could try verifying the local cache for the game.
Try running the game in compatibility mode, and while you are there maybe disable desktop composition (that helped a couple people with graphics issues in Vista/7 with Divinity 2).
In Windows Explorer browse to 'C:\Program Files (x86)\Steam\steamapps\common\divine_divinity' (for the Steam version), right click on div.exe and select Properties, switch to the Compatibility tab, check 'run this program in compatibility mode' and try Windows XP SP3.
Try emailing email@example.com, with a description of the problem and maybe a link to this topic.