Video card drivers may be whacked....try going to the mfr website and download and install the newest drivers. In the meantime, go to Control Panel/System/Performance and click Graphics link and move it down a notch or two in order to temporarily stabilize the mouse and video so you can travel long enough on the net to get what you need.

If that doesn't fix it, think about overheating inside the the case and clean out all the fans with compressed air and reseat the video card to make sure dust bunnies haven't built up around the slot (remove the card and reseat it). Last might be to replace your power supply if none of the above resolves the may be going south on you....and if you have to replace the power supply get one that has more wattage that what you're using now.