The USB port shutting down is a distinct possibility, my laptop did that until I changed the power settings in Windows. You can go into the power settings in windows and click on the plan your computer is using, once there you can click on the advanced settings and change how your USB ports act when the computer goes to sleep. Sorry I can't be anymore descriptive than that, but what setting it is or where it is at depends on what version of windows you're running and I think whether it's a laptop or desktop is also different. If you're computer literate at all though it shouldn't be hard to figure out.
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