Trying plugging into a different USB port if you are using a USB drive, the ports on the back of the computer usually work best. You can also try changing the drive letter. There are steps outlined in this thread that may help you. External HD No Longer Works With Computer
Someone else fixed the problem by doing this,...
“I had a similar problem. went to the properties for my ext hdd through device manager and changed the removal policy from the default quick removal to better performance and everything is working well now.
hope this helps some off you.”