I recently posted a few times on this forum seeking help but received no answer. I was having issues with my gaming PC which has i7m 2 x AMD 6970 factory OC going through displayport out to a 27" imac (used as target display) running at 1440p. I have not had any issues using this setup since 2011. As soon as i upgraded my drivers in Windows 7 to 15.7, screen went blank. I rolled back to Omega 14 drivers, worked again.
Then, after installing Windows 10, it updated to 15.7.1, again blank screen on 27". After a lot of fiddling, i realised that it was the 15.7 and 15.7.1 drivers. . I read somewhere to go back to the omega 14 drivers. I tried this, but windows 10 didn't seem to like the installer, the installer kept crashing. So in the end i rolled back to Windows 7, tried to 15.7.1 drivers, still no luck. I then uninstalled the 15.4.1 drivers and installed the 14 Omega drivers, and BAM! It works!! 27 inches of 1440p glory, all working again!!
I think i'll be waiting until AMD sorts out their drivers before upgrading.
I hope this helps some of you out there!