|Right click My Computer, or Computer;|
Either on your Desktop, or Start Menu.
Then click on Manage, or Properties.
Now click on Device Manager, or the Advanced System Options, or the Hardware tab, then the Device Manager.
Now simply right click on any of the hardwarez and click on: "Scan for Hardware changes"
Your USB should now work.
This problem also happens when you force shut down your computer alot, just resart and then shut down via the start menu power button, not the computer button