I have had this on my laptop as well and it was the graphics card, or rather the graphics card drivers. Try installing the latest version of driver (or re-installing the driver).
You may also want to try altering the refresh rate on the card (if you can) and or running at a different resolution.
Regards,
FWyg.
P.S. Doubt its anything sinister.
OOOOhhhhh, one more thing. Does this graphics glitch occur after your machine has been on for a long time or does it happen from startup?