I have an Nvidia card, and updated my drivers today. I don't have the "black box" issue anymroe and shadows seem to be showing up fine.
If it matters, I have a GTS 250 and I'm running Windows 7 in 64bit.
Yeah that fix nvidia_fix dont work for me =(
Currently I set the transparencies to software though and its fine.
There's another fix for graphical problems using the Application Compatibility Toolkit from Microsoft which can be found here: http://www.microsoft.com/downloads/en/details.aspx?displaylang=en&FamilyID=24da89e9-b581-47b0-b45e-492dd6da2971
Sadly I don't have the exact instructions for this workaround anymore, but i remember that by using the toolkit you had to add some "DirectDraw" thing to the Baldur's Gate exe. Maybe if you search for it you find the exact instructions somewhere...
EDIT: FOUND IT! :D
Here's the guide: http://www.shsforums.net/topic/30840-ie-games-and-nvidia-series-8-video-cards/page__st__60__p__432892&#entry432892
Just to note. Gave this a try. Seems to work. Thanks =)