i had the same issue with my 7850. but i found a solution today.
i hope i can describe it good enough in english, so here is what you have to do.
Go to device manager in control panel. then look for audio-, video- and game controller.
right click on AMD High Definition Audio Device or ATI HDMI Audio (if you installed Realteks ATI HDMI Audio driver
click on driver update and choose the 2nd (search driver on computer) and then list on computer.
choose High Definition Audio Device (its the driver from Microsoft) , do not choose from AMD.
ignore the warning and click on yes.
now it should be working, but without HDCP.
hope you can understand this and hope it helps...
greetings from germany