I have a user that periodically saves his work in a .zip file and writes it to his folder on the file server. This will work for a couple of times until he gets an error message that states, "Error: File not found or no read/write permission or sharing problem." I looked at the folder sharing properties, and everything there seems to be in order. Once the user gets the message, he cannot write over the files on the file server until the next day. Why does this happen and how can I fix the problem?