had the same problem, tried everything: had to quit a window
Hi: I have a Vaio and a Sony Bravia Tv, it worked at first but suddenly the HDMI icon was no more in the: SOUND-> play back devices window. Tried cable, troubleshooting, etc.
I had to undo a windows 7 update (restore) and the HDMI is agaun there.
Perhaps it is not neccessary to undo the update if you could find how to solve the conflict, but this worked.
Hope it helps.