macbook pro to HDTV losing connection.!!

Hi, I'm new to this forum and have a slight problem with my mac to TV connection which i hope you good people may be able to advise me on.

I have sync'd my macbook pro to my panasonic HDtv via a miniport cable/hdmi and TOSlink digital audio out.

I've connected the cables up via my onkoyo AV receiver in the correct manor,power up the mac, switch on the TV,select the correct hdmi input and the mac does display the picture and the av receiver outputs the sound but AFTER about 2 minutes or so it losses its signal and displays 'snow' on the tv and then the signal intermittently flickers back and forth (picture-snow-picture snow, etc) but the macs display's screen keeps its picture.!! I have also tried connecting the hdmi from the mini-port adaptor direct to the TV leaving the AV receiver out and its still the same.

any help is greatly appreciated thanks.

( if this is in the wrong section i apologise and could a mod please move it to the correct one)

Dave