Reports of USB-related problems have been circling for a few days. The issues seem to surround USB power - the receiver seems to use rather a lot of it, rendering other USB ports powerless and peripherals therefore unusable.
On the forums at Xbox.com, one user suggests restarting your computer and pressing the Sync button on the controller, but it seems not everyone is having luck solving the problem. And Microsoft has been less than helpful over the issue. We're waiting for a response.