That looks like a PS3 output issue. There's a thread with lots of PS3 setting information in the Blu-ray Players forum.
Meanwhile, the settings you mention on your system (PCM Stereo, DTS Re-encode, and so on) are output settings for the system's disc player. They won't have any effect on processing audio from external sources such as your PS3. And, yes, you have a 5.1 system with some of added processing on four channels that LG then calls 9.1. It is not 9.1, of course, which is nine channels.