|Symptoms like that are not normally caused by software problems.|
Make sure both displays are plugged in properly.
It's probably either caused by a flaky mouse or a poor connection of the card in it's slot.
If it's a corded mouse, try another mouse.
Unplug the case/power supply.
Power off your monitor.
Open up the case by removing the left panel as seen when you're looking at the front of the case.
Make sure all cards in slots are all the way down in their slots.
You could also try uplugging the video card and plugging it back in again, but be sure to install the screw that holds it down before restoring the AC power.