I had a problem using DVDshrink with a Western Digital MY Book 3TB external USB 3 drive.
Tested on usb 2 connection, win 7 64bit machine.
Works fine to other usb drives on the machine.
Did a google and found other people with similar issues with 3TB drives (don't think it's limited to Western Digital).
Anyone got it to work on a 3TB drive (or should we give up on this idea)?