A long discussion ended abruptly when the owner found a speck of dust in the optical receiver of one of their systems. This does happen and why optical isn't as sure a connection as we had hoped. Try your canned air with a short blast into the optical receivers.
There is an issue with optical output from all HDTVs. For a lot of content it will be stereo and since that is well discussed I'll stop here.
I recently bought this tv but am having problems with the sound dropping out when the tv is connected by a optical digital cable to my samsung surround sound system. If i connect to my vt vision box this does not occur but i then cant access the hd channels on freeview in surround sound. i have had the tv replaced by the company i purchased it from and also samsung have replaced the board in the new tv but this is still occurring and driving me insane. i have tried the exact same set up on my daughters tv and it works fine. is it possible that my home cinema system and tv are not compatible? they should be as they r both anynet+. Anysuggestions would be welcome thanks.