solved: No sound from sony vaio windows 7 to TV with HDMI
I had the same problem, and in addition my HDMI audio indicated that it was not connected at all. Over the wkend I solved it doing 2 things:
1. Windows 7 sometimes doesn't choose the correct driver for my device. Driver indicated as "sigmatel high definition audio codec", in my case. I had to go to Device Manager -> Sound Drivers -> Update Driver Software -> Browse my comp for drivers -> Let me pick from a list of drivers. Choose the driver that's not a "CODEC" driver but a standard device driver. It reinstalls the proper drivers.
2. Make sure when connected to TV, set the new "Hight definition audio device" to default as indicated in other posts. REMOVE/RESTORE this option back to laptop drivers when you are through with the HDMI connection on you laptop!
Hope this helps all!