No Picture

Forgive me if this is not the correct thread. Feel free to move if so.

I have a home entertainment system, whereby my TV is routed through my computer. It's viewed through the Windows Media Centre which enables me to pause 'live' tv and record in a manner similar to Sky Plus.

Anyway, as I've done numerous times before, I set a recording for the middle of last night as I was sleeping. Once I had set this up, I put the TV screen on 'Sleep' mode and as usual the screen blacks out and off I go to bed.

Normally, all I need to do to bring the screen back is click my mouse or turn on the Media Centre. This morning however, the screen just wouldn't reappear. It has remained blacked out. I turned on the Media Centre (via remote) and as I knew it was on 'pre-recorded TV' I clicked and played the most recent recording. It started with perfect sound, but no picture.

After trying various things, I took the risk of just turning off the entire system via pulling the plug, hoping it might have readjusted itself when I power up again. No joy. Repeated, but left it for a few hours. Same result.

Is there any obvious thing I might be overlooking or do I need to have an expert look at it? It seems to be purely a picture issue.

Thanks in advance.