ATI Radeon 4870 slowing down ( intermittent)

Hello

I did start another similar post few weeks ago, but problem still not resolve

Intermitent, Graphic card is slowing down

Occasionally, my Asus EAH4870 DK card is slowing down. My system use 4 screen monitors. 2 are driven by the GPU card, the others 2 are driven with USB external graphic card

Once in a while, about 3 time poer day, my screen driven by my Asus card, slow down. The refresh is erratic. When I move the mouse over my screen, it did not follow the movement as fast as it should.

To resolve the problem, I unplugged the DVI cable from one of the screen while PC is running. Few second later, I re plug the DVI cable and all came back to normal.

Since the PC was running while I unplug the cable and re - plugging it, I don't think that is is related to a temperature problem. Look like the driver are restarted when I plug it back.

Could it be a Windows 7 problem?

What could cause that?. Any idea how to resolve the problem?

I don't have another GPU card, so it is difficult to determine if it is a physical problem
or a driver one

Martin

Intermitent, Graphic card is slowing down