|If shutting down and rebooting fixes the problem (temporarily at least) then it is not the monitor and probably one of these issues:|
Bad memory. Run memtest86 to test your memory.
Underpowered (power supply does not have sufficient Wattage, or sufficient amperage on the 12 volt rail(s)) or weakening power supply (causing video card to lock up due to lack of sufficient power at peak loads). Post detailed system specs.
Bad video card.
You have to be a little bit crazy to keep you from going insane.