Hi - enjoying my new TiVo HD with Comcast cable (SA S-cablecards all working great). I have an incredibly obnoxious issue where very frequently a LOUD ticking sound comes blasting thru my speakers. It happens every time I switch screen resolution (for example going to the TiVo center from TV). It ALSO happens whenever I resume playback from FF. I can make this behavior stop if I go into Settings and change Audio to PCM instead of Dolby Digital. I have my TiVo HD hooked up to my receiver (Pioneer VSX-D607S) via optical. Has anyone else seen this? Any suggestions? I am forced to leave DD off which I hate to do! Thanks!