Thanks, in error the mouse type cited was wrong due to fact on first reply I had the "parts slip" in front of me and it indicated incorrectly "Logitech wheel mouse" Actually when I checked original equipment mouse and hardware setting on computer it turns to be a wheel mouse but Microsoft PS/2 mouse. No logitech programs loaded on computer. Fiver years of experience with this intermittent problem, sudden screen blank shut down ( BCCode 50), my estimation is it has happened at most 200 times but always right after a mouse double click. At first it happened very infrequently, for example once every 4-6 weeks, but recently it has been happening more often. If I stop using the mouse, which goes with device driver removal, I do not expect to see the problem but also can't get work done. FYI I typically turn off computer when not using it but one time, fairly recently, I forgot to turn it off and left it on continuous for several days and the problem did not occur.