Audio problem, please help?

[Viking]

I have an audio problem when I upgrade FW to 1.33N or any new FW like latest HD2-R3. I am using HDMI cable. In main menu and during the steps to start the movies, the TV just keeps make buzzing noise. The problem stays there with different HDMI cable. But when I use 1.30N, it is fine. If I change to RCA cables it is fine also. Any experts can check for me where is the problem. I got help here before and hope some one can help me again. As always I appreciate your help.