Does the drive function properly when the card reader isn't connected to the computer? That is can you actually transfer files to/from the drive?
If it doesn't work, you can try drive cleanup. Run it with the -T option first to see what changes it will make. Be sure that your external drive and card reader are disconnected from the computer when you run it. If you don't feel comfortable using it, I understand. I have used this in the past and it worked for me. Just so you know, if you do run this, any usb device that was previously plugged in will act like it's the first time being used on the computer. That is, you will see the "new hardware found" dialog when you plug your drive or any other deivce that wasn't connected at the time you ran the program.http://www.uwe-sieber.de/drivetools_e.html#drivecleanup