Why did my USB 1.1 devices stop working after I updated a driver for a USB 2.0 device?

A. This problem is a known issue with Windows XP Service Pack 1 (SP1) and is caused when you use Device Manager to update the driver. To resolve the problem, restart the computer or open Device Manager, select the Action menu, then click Scan For Hardware Changes. Obviously, if you're using a USB mouse and keyboard, these devices will stop working, which might prevent you from cleanly shutting down your machine.