There was a mysterious type of action in a thread the other week, basically you turn off the computer at the wall, do not unplug, then connect and disconnect the USB 6 or 7 times and then restart. It worked for the problem at that time but nobody knows why.
Yeah Biotech I was involved in that, no one has given a satisfactory explanation as to why it worked, heres the link click here you can see the solution that anniesboy68 gave on page 2 and this was it "Try switching the computer off and at the wall. Then hold the start switch in for 30 seconds or more, and then re boot. Just try!!!!!"