I expect the keyboard and receiver got mixedup at some point...
so both are now useless!?
What an absolutely rubbish design from a user point of view, but a great one when it comes to Microsoft scamming more money out of people as these dongles are easily lost, I don't usually buy Microsoft hardware (or software!) I got this keyboard and dongle in a job lot of bit, this has reinforced my decision never to buy microsoft and I'll advise anyone else not to buy microsoft hardware either.
Thanks for your help, my problem is not resolved but it sound like there isn't any way to fix it.