In D2:ED, one person with 64 bit Windows 7 had this problem, but fixed it by installing DirectX 9. A couple people just had some textures that were transparent, fixed by updating their graphics drivers. One person ran into this with the D2:ED demo, but lowering the game resolution eliminated the transparency.
Try running the game as administrator, and in the compatibility options disable desktop composition (in Vista/7).
[PC] Support FAQ - The Dragon Knight SagaFirst Aid Kit for Divinity IIFirst Aid : when Div2 does not start or crashes