It could be a sync issue. HDMI sends audio and video and also communications between devices. Every 2 seconds there is a HDCP signal sent from source to display and sometimes the source doesn't always send it correctly. I ran into a problem with sony tv's awhile back with HDMI. Got snow on the screen from the dvd (HDMI) input when you would switch to it, but if you would switch to different tv input and then back to dvd it would work fine. Try and have a local dealer help you out, could be a number of different issues.
We have a Sony Bravia that we purchase Nov 2007. Our problem is that when we use the HDMI cable (hooked up to our digital Motorolla box) the audio is lousy -- it will drop out for a few seconds at a time, and the volume is greatly inconsistent among the channels. I would say the audio drop-out happens about once or twice in an hour. If we use just the regular RCA cables instead, there are no audio problems. What is the source of our problem and what is the best way to fix it? Many thanks for advice/tips!