Third Monitor stopped working

I have 2 HD6950 GPUs running crossfired with 3 monitors. I have been running these together just fine for a few months.
This morning they were working fine. Then i ran a few errands, one involving picking up a new wireless logitech keyboard and mouse. Once i came back home and installed the new KB and mouse i turned the pc on and now the monitor i had connected from DVI via mini-displayport adapter no longer works. The power is on but no picture shows. I went into catalyst and it does not show the third monitor enabled.

How did this happen? More importantly, anyone know how to fix it?

Thank you VERY much for any advice.