The other day I found that my mouse and keyboard weren't working.  I checked the usb connections and tried them in several different combinations in the 5 usb ports on the back of the tower.  Still nothing worked.  However, if I connect the usb to firewire cable from the tower to the back of my monitor, then I can use the two usb ports on the side of my monitor for my keyboard.  Also, my printer has no problems with any of these usb connections, but my ipod, camera, and palm pilot don't work in the rear ports.  When I plug my ipod into a rear port, it charges like the port has power, but I cannot sync with Itunes.  I have tried to uninstall and reinstall all the Usb root hubs, but that did not fix it, and the diagnostic test said nothing was wrong.  It is weird that this just happened, with no apparent cause.  Does anyone know what I can do to fix it?  With only two working usb ports on the side of the monitor, it is impossible to use all the gadgets I normally use.  Thanks.