If you added a new USB device recently, it may be faulty - unplug all devices and restart, then add them from the time you first plugged them in, until the system hangs
James Allanson, January 2006
make sure the usb ports are enabled within the bios seup pages,hold down delete during startup
nigel, November 2005
have you tried reinstalling the motherboard drivers?
aa, May 2005
edit
I can answer this question...
my computer has lost any contact with its usb ports?
