Long shot here, sometimes in Windows it turns off the usb ports to save power worth checking out?
Goto My Computer right click then into device manager goto the section with the usb ports and check on properties, on one of the tabs you may have a checked option to save power, uncheck for each one and apply.
Number two your usb drivers are installed right? and the lead is not cricked, or frayed anywhere? also the teeth on the usb connector is not obsctructed or damaged?
Finally hit the thing... worked for me a few times