Sound cutting out... Help plz!

[JaysDomain]

When the sound cuts out on my Sony AV receiver using DD5.1 (bitstream), does this mean it cannot handle the bandwidth or what?
It will almost always do it during an action scene, and sometimes at random.
When I change it over to Linear PCM it works fine, but my receiver (on autodetect) changes over to stereo and takes away the DD light, so I lose my 5.1 surround.

I am using a PS3 with optical to a Sony 6.1 receiver (it does not support HDMI).

I am getting a new receiver this year (probably the new Sony when its released), but I would like to get the best sound I can for now; can anybody help me figure out a fix for now?

Thanks!