I'm having this problem with a new kit of wireless mouse & keyboard from microsoft. It was working just fine, but now only the keyboard work. There's no ON/OFF button to turn off the mouse. There's a little switch that is activated if you place the USB dongle under the mouse, but this switch is not pressed.
There's no led on this model so there's no way to say if the mouse is On or Off.
I've changed the batteries of course: still not working.
I've unplugged the dongle, and plugged it back in the same port: still not working
I've unplugged the dongle and plugged it in another USB port... same problem.
The keyboard still work, but the mouse is dead.
There's no yellow icon showing a problem in the device manager.
This computer is running under Windows Vista.
P.S: I've just tested the kit on another computer, same problem... keyboard is working, mouse is dead. So i guess it's only dead and i got to return it?