Is there any switch on the flash drive? Is the drive full? If not it might be an idea to try uninstalling and reinstalling the driver. To do that try:
- Plug in the flash drive
- Right click on My Computer
- Choose Properties
- Switch to the hardware tab
- There should be a button like "Device Manager". Click on this.
- Find your flash drive on this list. Right click on it and choose uninstall.
- Unplug the flash drive, wait a few seconds then plug it back in.
- You should now get a new hardware wizard dialog from which you can reinstall the drivers.