Any chance this could be power supply issue (i.e. my card cannot get the prerequisite power to produce an adequate display on the second screen)?
For some reason that thought occurred to me, so I entered my rig into a PSU calculator on a few different sites. Although the recommended PSU wattage varied, the ultimate result was the same... I am under powered with my 750W.
The recommended ranges were from 849W to 1250W.
I would have Recommended a 750w if you were using one card. But if you are doing SLI or Crossfire you are going to need at least 1250W. I would say. But if you are OCing then that should still give you a bit of Power to play with, but remember when the psu gets older it drops power.
[Edited by ServiusTheBear, 11/6/2013 3:34:31 AM]