what about a hardware driver issue? perhaps that is causing the bluescreen to happen. I would check out "event viewer" if you are using windows xp or later. If there is nothing in event viewer relating to drivers issues, make sure your computer is not overheating by using a program like "realtemp" or something similar to monitor your temps.

as others have stated, running "memtest+" will check for memory errors in dos, and are you sure the overclock is stable? maybe upping the cpu voltage a tad will help with the system being stable.