That looks like a typical memory corruption problem but I'm not sure if it's possible to affect only one screen like that. If you have overclocked your displaycard, remove the overclocks before doing anything else.
Anyway you can easily check the monitor and cable by plugging one of the other screens to that DVI slot. If they go bad, it's the card. If they won't go bad then it's the cable or the screen.
Just make sure you'll plug all of the monitors back for the test so you can use full desktop resolution and all of the videomemory you usually do.