It's definitely the cards, and we've tried it with multiple Windows 7 Optiplex 760/780 machines running both 32 and 64 bit Win7 - they all crash. Has anyone else had this experience?

The OptiPlex 760 is the mainstream workhorse of the line ... All form factors save the USFF support up to 8GB of RAM. The USFF machine supports up to 4GB. Optional graphics include ATI Radeon ...

Those each sport base configurations that include a 3.0GHz Core 2 Duo processor, 1GB of RAM ... out the $399 OptiPlex FX160 thin client PC, and updated versions of its OptiPlex 760 and OptiPlex ...