After upgrading to the Win7x64 and SolidWorks 2010 SP2.1 for 64 bit my screen would often times go black. Then it seemed I couldn't keep a session open for five minutes without a crash and a ntdll.dll fault.
My hero came in the form of a service tech at my VAR.
It seems that just updating the NVIDIA card from DELL didn't completely upgrade the driver. There is a NVIDIA supplemental driver that you need AFTER you update the FX1600m driver
Once loaded paying careful attention to the instructions not only does SW run like a champ, but it seems everything is running faster and better.
Hope this can help if you have a similar setup.