Lost most saved recordings & record doesn't work every time?

When I try to play recordings I just get a blue screen with the play/pause icon in the bottom left corner of the screen.

The thing is, not all the recordings have disappeared, some are still okay and can still be viewed perfectly (both normal & HD)
Some of the missing recordings are from months ago and have been watched many times before, while others are only days old.
I have tried to record new programmes but have only had very limited success. Some of the shows record fine while many others don't and it doesn't seem to matter whether it is set up to record in HD or not.
Any ideas what this problem could be and how I can fix it? Cheers.

Pete
January 2011