Sounds like you either have a fault box or faulty lnb (the bit on the dish)
Is it a Sky+/Sky+HD box?
Do you have 2 inputs from the dish to the box?
Could be that 1 input is faulty.
Try this as a test. With the box switched OFF at the wall otherwise you will damage the lnb. Disconnect the 2 inputs from the dish, and reconnect the one that was on lnb2 to lnb1. Leave the other disconnected for now.
What you have done is take the cable that was the second feed and make it the first feed.
If the box works fine like this, then could be the lnb. Now again with the power OFF reconnect the unconnected cable to the lnb2 input.
Now try the box, record something and try watchng something else - if you get the technical fault then you definately have a fault.
A neighbour had problems with her Sky box - which only had one feed connected, so when I swapped them over the box worked again. She had booked an engineer from Sky, when he came he replaced her dish and lnb.