next time it happens I will post logs. I personally believe it is a intermittant codec issue but I could be very well wrong. I have never used FFDShow Audio codec only ever AC3Filter.
I too was getting no sound on channel changes, for one channel it happened every time I changed to it for the first time. Can confirm changing the audio codec to ffdshow from the mediaportal default seems to have eliminated this. Am also using the Power DVD video codec and RC2 in Australia without any problems.
I got it to happen and I can say there is absolutely nothing in the logs at the time I go silence.
scenario was
watching channel for over 30 minutes with no problems, between ads I lost sound, My Amplifier was shoing MPEG stream, if I not watching TV is not the default so it was getting some sort of signal but could not interpret it i am assuming. Log files show nothing (Mp.log,tvstream, error.log). This must be a codec thing or graph rebuilding possibly???? After that it has not happened for 2 days now and I have changed nothing. real intermittant and not a real big deal but a nice to fix fault if i can....
Seems to have worked for most people - I certainly haven't had any problems with sound drop-outs since using ffdshow. As to whether it's the only fix, I don't know. In terms of configuring it, I just leave all the devices, etc. as the default.