Not sure if you're using Mac or PC. If it's PC, this fix should work, and will take less than 5 minutes:
1. Go to Device Manager
Vista: Start -> Control Panel -> Classic View -> Double-click "Device Manager" icon
XP: Start -> Right-click My Computer -> Choose "Properties" -> Click the "Hardware" tab -> Click "Device Manager" button
2. In the list, expand "Universal Serial Bus controllers"
3. A sub-list opens up. Go through the sub-list doing the following to each item:
i) Double-Click it
ii) Go to the "Power Management" tab, if there is one, and uncheck "allow the computer to turn off this device to save power"
(some items won't have a power management tab, so just skip this step for those items)
iii) Click OK
4. Close Device Manager, close Control Panel, restart the computer.
That should sort you out :>
-Annikk