Bluetooth mouse/keyboard - USB error after sleep

I am using Vista HP and a Microsoft Bluetooth mouse and keyboard.

Everything is fine until Vista wakes from sleep.

When I am presented with the password screen Vista takes about 1 minute
before the keyboard and mouse become functional.

After entering my password Vista opens but then I am presented with an error
"Unknown USB Device".

This happens on all my machines, all of the time after sleep (all exactly
the same machines and config).

If I remove the BT dongle and put a regular mouse and keyboard in, the
problem goes away.

I am using the latest MS Vista drivers for the keyboard and mouse.

What could be the problem?