Hi guys, thought I would become a member just to post this as I think I might have found the source of this problem, at least for some (including me). As when reading this thread I had a bit of a realisation. @i-rock-socks said you still get audio to the headphones, so do I, and they are connected via optical cable while the TV is via HDMI, like most are I assume. I tend to turn my playstation on followed by my TV, and dependent on how long this takes me, I get the no audio problem (from the TV).

So, my theory is, that the playstation doesn't output sound to the TV as it only picks up the headphone output on startup, as the TV isn't on yet. The trick is, turn on your TV first!