I had a simular issue - random blue screens while 5 boxing and I never had the program while 2 boxing. I would also log off WOW for the night and turn off my monitors, to come back in the morning and see the machine had blue screened. Interestingly this only happened following WOW and keyclone.

This was running with 8 gigs of RAM and a dual core. Last weekend I upgraded to a quad Q9550 (2.83ghz before O/Cing) and it's ran all 5 instances perfectly now with no crashes during WOW or post-wow. I lubs my new CPU

-Clov