I've had this issue too, the only way I could make this work on W7 was using, one DVI, one HDMI and DisplayPort (im using a pasive DisplayPort adapter to DVI)
Also, its only working with the controller version 184.108.40.206. Im downloading right now the new beta version 14.6 to try if it works. With the other new releases it wont work.
Btw, im using the r9 270x with 4gb.
I hope I have helped you, and I also hope AMD will solve this issue.
EDIT: Its also working with the new 14.6 Beta driver on W7.
01:28 PM by