Here's what I have found. The problem only happens after I put the TV on standby using my Sky TV remote control. Then the TV randomly turns off / on etc. This has happened to me twice and has been fixed the same way. Make sure the TV is on before starting the process below...
-Turn off the TV using the Philips remote (so it is in stand by) and wait for the normal click noise from the TV (a double click from mine).
-Turn the TV back on with the Philips remote. Wait for the click to confirm it's on and wait for any lights to stop flashing.
-Turn off the TV again with the remote so it's in stand by again.
-Then turn off the power to the set by unplugging it. Leave unplugged for at least a minute.
-Plug the TV back in, wait for it to settle down then turn on using the 'on' button on the TV (don't use the remote).
This reset process is direct from Philips UK and works on my set every time. Finally - don't put the TV into standby using a remote control (especially any non-Philips remote) and it should not happen again!