D|S is very particular about your video card and openGL.  I'm not sure why, because it doesn't utlize the card memory during rendering (that's all on your system memory) but does utilize the card memory for the Viewport display. 

Truthfully, I designed my system to work with the Adobe CS4 Extended Package because I design Flash, Video and graphics.  The video card I bought was the lowest end one that Adobe would accept for use with After Effects, but was considered high end for D|S.