A repair install or sfc didn't fix that problem?
Unfortunately, No. In fact, I think this computer might be a lemon. We have another GX620 that's performing fine with the exact same setup. Initially, BSOD's were being caused by a video card. Installed a new video card and started getting BSOD's with new error codes.

This current BSOD is being caused by a INVALID_WORK_QUEUE_ITEM related to ntoskrnl.exe. I've ran SFC, Dell Crash Analysis Tool, Dell Driver Reset Tool, Updated all the drivers from Dell, MemTest86 to name a few.

I've opened up the box, cleaned out everything, made sure all the cards were seated correctly, blah blah blah. I still think it may be video driver related but, I've uninstalled and re-installed the video drivers more than once.