I'm no computer expert, but I can offer the following suggestions:

Have you updated your video card drivers?

Gotten your latest MS updates?

Done a virus and adware scan?

Defragged your computer?

Do you have Quicktime installed?

Maybe the computer is overheating?

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi