I suspect from ante1's mention of watching the man install the ram, that this box was made by someone local...an iffy proposition at best (both boxes that I had someone make for me were trash,,until I rebuilt them..and the 2 that I've made myself work just fine)

it just might be a ram issue, though at this point I'm leaning more toward agreement with driver conflicts..also, a virus/trojan/malware just might cause this crap, hence doing a full scan would be a damn good idea...