All of my USBs stopped working. System information shows them. Manager says they are working ok. Troubleshooting can't find the problem. I'm using a 4 year old Toshiba laptop as a tower and running a keyboard, mouse, scanner, printer and misc. on USB connections (some on a hub). One time when I rebooted they went active but then next time I hibernated I lost them again.

Here is a general guide as a first step:

http://support.microsoft.com/kb/310575