To upload a file, you have two buttons:
"Upload" and "Cancel"
(Or something like that, I'm using another language than English for my interface)
When the file to upload is big, I do not wait in front of my browser for the end of the upload process... then I often forget to unlock the file.
It would be very useful to have a third button : "Upload and Unlock" that unlocks the file when the uploading process is done.