>In the middle of a transfer into a USB key, I got a message files were no longer being able to be copied. When I try to do another test, I now have a message stating the disk is protected. What can cause a USB key to become protected by itself?

Not sure if it is the same problem, but I have a similar issue with shares, freaking annoying windows "feature" as far as I can tell...

It happened to me with different programs so it is not related to one product. For example I have a program and several dlls, I compile the program in my computer, put the exe and the dlls in a share, then go to a different computer, run the program from said share, find a bug, of course it had a bug. So I close the program and rebuild the exe on the development computer, move the files to the share and voila, after copying a number of files I've got the message that I do not have rights to copy to the share!!! Anyways, I found out that windows kept some files opened even after closing the exe (sometimes it is even the exe that is not being released!), so I need to log-off from the computer that ran the exe to release it before copying the files back. Of course I stopped running the programs from the shares and making a local copy first...

Anyways, I think you might have a different view of the same problem, one of the files you are copying to the USB is in use or at least Windows thinks it is in use and the message is misleading