It sound like your using the HDMI output to the TV and you analog to your audio receiver?
If this is the case?... Try using the digital audio output from the TV. You can do this only if you setup your HDMI device to send the audio via the HDMI output (you can find this under Audio settings in the Setup menu). Now you just run a Digital audio cable from your TV (Coaxial or Optical) to your receiver. If you have more than on device (such as a DVD Player, Cable box, Gaming system,Etc...) your now setup to only changing the TV input and leaving the receiver on one input (usually TV).
This allows the timing of the audio and the picture to stay in sync.
If your not running your system using HDMI it would help letting me know how it is setup?
Just drop me a line and I'll look into it for you.
Hope I helped.
