Hmmm ...
I agree with the first response, i.e., check the vidcard to make certain it is nice and secure (this issue reminds me of a Savage vidcard on a Soyo board that required me to hit reset each
first time it was booted ... then it would stay on fine). ... also check the cable connections.
Presumably this problem did not rear its ugly head before the Phillip's monitor install?
(1) What video card is being used in your mom's computer?
(2) What Power Option settings are being used on that computer?
I lean towards the "not properly seated vidcard" as the culprit.
Brangwen