I encountered my first hiccup using the HDMI switch last night when trying to view a movie recorded on the free weekend Starz preview, when I selected "start over" a warning screen came up advising me that the connection I was using did not support HDCP and I must connect in a different way to continue. Tried several times, but a no go. So I had to pull my HDMI from the switch and connect the TV direct to the Hopper and the optical cable from the switch and into the Hopper and then it worked fine throughout. The audio dropout issue surfaced again immediately when fast forwarding to the beginning of the movie, but once audio was playing it stayed locked the rest of the movie since there are no commercials.
Could this be your HDMI cable. Could be a problem with the cable. Just guessing.