Digital sound not working on some demos

i have an optical cable going from my ps3 to my receiver and only when i play the simpson or skate demo my receiver will say error and not play the digital sound but any other game i play including some demos it works find. Does anyone else have this problem?

I find when i hook it up to my grandpas bravia it makes a loud noise going out and into games and alot of the times the sound is WAY off sync.

is dts the same as dobly digital?Esgabaldon

NO!