My first thought is a faulty video card. But, you say you swapped the cables around. Have you also tested that DVI port with one of the other monitors to see if the problem migrates to the other monitor, too? That would likely isolate whether it's a possible faulty port on the video card.
That was my thought as well, but when eyefinity is not enabled that connected monitor appears to work perfectly. Does the signal or anything change when turning eyefinity on?
I think I will remove the current drivers and reinstall, if that doesn't work I might just swap the two cards around and see if there is a difference.