FLZapped
If you are running Win 7, you have to go into the advanced power settings under "change plan" and shut off the feature that allows the USB port to be shut off.

tlw
Not only does USB suspend have to be disabled in power settings, to get rid of it completely you also need to right click on all the USB hubs/ports in Windows device manager, select "properties" and deselect the tick-box on one of the properties tags that tells Windows to put it to sleep.

Windows has been very determined to put USB into power-saving suspend since Vista.