If your card is under warranty (usually 2 or 3 years, sometimes longer) you can possibly get it repaired. But it kinda sounds like it's either the card or drivers.
Have you changed drivers around the time the problem began? Do you have any other programs running (my wife's computer has jitters when she has firefox open for some reason, could be similar)?
Do you have the ability to try VGA, it could be a problem with the digital communication, and analog may not have the issue (to determine if the card has an issue with DVI and HDMI).
i dont know how to change drivers, and the card doesnt support VGA