Depois de 3 horas frustrantes tentando todas as dicas na net, encontrei a resposta : Tente isto:
This finally fixed it for me: Device
Manager - Open System Devices, you
will find a Bluetooth HID Device.
Double Click it, open Driver tab and
click "Update Driver" Select Browse my
Computer, then "Let me Pick". It
should now show TWO compatible drivers
with exactly the same name. One of
them is the Microsoft one, one is the
non-working Chinese ****. Install one
of them and see if the driver
properties changed to the right
(Microsoft) driver. If not, try again
with the other one. For me, the
Microsoft driver was the first one in
the list, but this may be different
for you. Wow, an annoying and intense
hour of trouble shooting finally
over...
O problema está relacionado à versão chinesa do driver que o Windows Update mais recente aplica e interrompe o funcionamento do teclado.
Finalmente, posso digitar isso usando um teclado Apple Wireless Keyboard no meu PC com Windows 7 de 64 bits!