I don't know if the card is the issue. I have an ATI card and I don't see your problems. The OpenGL libraries (or other system software) work with the card to allow more-or-less rapid refresh in various preview modes, but it sounds like your problems are related to insufficient RAM and possibly excessive use of special characters or bad names in the shaders/textures in the imported files.

If you are somehow selecting lights or cameras with "Select All", I can see how the box would be huge. So you could try selecting various items in the sequencer tray instead, either by collapsing a sub-list or by drag-selecting.