Had the PVR9300T for a couple of years. Recently, it has started to freeze up when fast-forwarding or rewinding recordings and live tv. It did this yesterday and would not respond to the remote control for several minutes, so I disconnected the box. On reconnecting, the box starts to load (version a4.39) but cannot get past the loading screen and connect to the tv. The screen goes blank, then the box tries to reload a few minutes later and fails. If it cannot load and connect, then I cannot access the menu or recordings.
Help!

Have you tried the 'help' you were given here?

Yes, sorry wasn't doubting your advice!
Disconnecting the aerial had no effect, so before I disconnected the hard drive, I just wanted to see if there were any other options...

The hard drive has a thick red lead and a black/yellow/red triple lead. Do I disconnect both?

Disconnect both.

I was going to post yesterday with a similar suggestion to Martin's but your problem sounds slightly different to the known problem. That problem is where the machine is in a continuous re-boot cycle whereas you say yours re-boots after a time delay. Sorry no other suggestions.