Microsoft Wireless Keyboard & Mouse Not working

Hi,
My vista machine had an unexpected restart due to a power fluctuation. Now
when it starts the keybaord and mouse do not work.
The keboard works at the POST and at the F8 point where you can select the
safe boot, normal start etc.
I have tried safe mode and normal mode and get to the login screen and the
keyboard does not let me put the password in.
When I push the f lock key on the keyboard I can see the light come on at
the reciever whch means that the keyboard is connected OK.

Can anyone please help......

Thanks
Frank