usb memory key problem

I am trying to use knoppix to transfer files from a windows installation to a usb memory key. Knoppix mounts the memory key and I can see all the files on the key, but when I try to copy from the hard drive to the key I get "could not write to /mt/usba1/filename." I get the same problem trying to copy from the key to the hd. I can copy from the hd and memory key to a floppy, but not to either device from a floppy. Any help would be very much appreciated.

After verifying that you can see the files on the USB memory stick, right click on the icon and go to actions > change read/write mode.

Thank you!