After plugging the pendrive in the device, go to device manager (In run type "devmgmt.msc") In Device manager go to "Universal serial bus controllers". It should list the storage devices that you have connected to your PC. Right click and then click "Uninstall. Remove the pendrive and restart your system.
Try connecting the device again, I think this should solve the problem.
If you don't know where you go, get back where you come.......