Just tossing this out there, in case anyone else runs up against it...
For the past three or four months, I've been running my PS3 through a DA5400ES with no problems. My girlfriend and I are living together and there's no room for my projector in the apartment (in classifieds btw; wink wink). So I've been limited to her LCD. To keep it simple, HDMI straight into the tv for straightforwardness for her. And optical-out of the cable box and PS3 for optional audio.
We borrowed a DVD from a friend and were watching it tonight when I started getting dropouts. I chalked it up to a friend who probably wasn't into the same level of care that I practice. But after the DVD, I popped on some Netflix. Same thing.
Fast forward through all of the standard troubleshooting and what I noticed was; The Sony receiver will temporarily display an audio format when it locks onto one. When I was in the PS3 UI and would button-left or button-right across the menu (for those familiar, there's an optional 'tick' sound), the receiver would display, for a fraction of a second, LINEAR PCM. If I held down the left or right button, thereby initiating rapid ticks, the receiver would rapidly flash up the format, the same number of times there were ticks. Even more random, when I stopped, the receiver would display dashes across the screen for a second or two.
Like I said, all of the standard troubleshooting. I know the input on the receiver is good. The three or four Toslink cables that I threw at it are good. HDMI audio, out of the PS3, is good. Even tried a factory reset of the OS, to be sure it wasn't on the software side. It just seems like this hardware is failing! So if anyone comes across this, now you know.