Well, let first assume it as
hardware problem, please try it on another usb port, if possible use another cable.
After this,
restore you system to
previous state when it was working. Suppose if it was working yesterday, then restore it to day before yesterday.
It's also important to revert your system, if you have made recent changes to your system, please try to restore them, like
software update, drivers update, etc..
After you've
restored your system, please run a registry cleaner
(click here to download a free registry cleaner) and a full
antivirus scan using an updated
antivirus.
If you see no changes and effects after these, then we need to work with the registry.
Please let me know after you are done.
Thanks.
Awaiting..