Last weekend I decided to free up one of my TVs HDMI inputs in preparation for a HD STB and routed my HDMIs via my HT amp. I noticed that if the PCH was now powered up without the amp being turned on then there was no input from the PCH and it had to be rebooted. Going TV+0 (auto gave a crappy picture. (The PCH was set to auto sense on boot up)
I discovered via trial and error if I set the PCH to output 720P / 60 then the PCH would always output to the TV regardless of whether the HT amp was on or not at the time. The other bonus is that the PQ looks far better that 720P/50 and the picture formatting is now correct and I don't have to press the Zoom button changing from 2.35:1 and 16:9.
It would appear that the Sony TVs sold here are much more at home with a 60 Hz rather than 50Hz picture being fed to it. I guess as the PCH is designed in the US which uses 60Hz HD signals then this makes sense. A bit like in then old days feeding a NTSC signal to a TV via PAL60 rather than native NTSC. The native signal was always better..