I have the same problem. Sky say it was probably due to a power cut.
I tried the reset procedure as follows:
Hold down the back-up button on the sky box for 10 seconds.
While holding down the back-up button disconnect the power at the plug or from the back of the sky box with the other hand whilst still holding the back-up button.
After the power has been off for 10 seconds, plug the power back in while still holding the back-up button for up to 60 seconds.
This procedure I was told resets the unit 95% of the time.
I am of the 5%.
Any more suggestions please let me know.
Sky say I have to buy a new box or get a technician out to fix it for £65.
Jon
November 2010