Originally Posted by **********

I had the same problem with ATI cards. 2 monitor setup worked well for a long time then one of them started acting buggy.

First make sure that the refresh rate is at 60hz for each monitor, or set to whatever the manufacturer wants.

Next, swap the monitors to make sure that the problem is not one of the monitors themselves. Try also swapping the data or rgb cables for new cables.

Get the latest drivers for your card & monitor, make sure all of that is up to date.

If the problem still continues, you may have no choice but to swap the graphcs card out for a new one.