How much memory is in your machine? This is a common problem with Inventor on memory-challenged PCs (< 512 MB), even with "certified" graphics cards/drivers.
Does this happen with a really small file, say a basic rectanglular object with no features?
What display hardware/driver settings appear in the Display control panel properties? (Look on the Settings tab)
BTW, while looking at Autodesk's help files on this, I ran across
this interesting comparison of memory usage vs. graphics adapter.