i've been running a 2xHD5970 crossfire for more than a year without any issue.
Yesterday i installed a 3 Dell U2412M eyefinity setup.
It worked fine for a couple of hour. I reboot more than once.
Then suddenly, after a Win reboot, it wasn't showing anything.
POST sounded fine, so i changed the output to the second 5970 and everything was showing on the 3 displays.
But, sadly, the main card, on GPU-Z, showed only one GPU (not recognized by CCC).
Is there something I can try? It's like the master GPU has gone, while the slave is still alive (so no POST error even with just that card plugged, but no video output), but useless since i cannot enable crossfire in ccc.