This is good advice. Try a planner rebuild, after the latest software upgrade there are a lot of people with problems, google sky box not recording etc and you will find a lot of info. If the rebuild doesn't work try a full reset, this will delete all recordings, but I doubt that will be of concern, if you're considering changing the box anyway.
You can find out how to do these if you google sky planner rebuild/reset.
If none of that works ring sky and say you can't afford to buy a new box and that you'll have to cancel. We got a new 2TB HD + box for around £49, worth a go?
Good luck, make sure you push it.
Not sure you would lose your recordings. Can't recall I'll lost mine when I did it. It was a while ago mind you