Files say they are open, when they arent

When one of my users tries to open a file in there home directory, which they only have access to. The file says it is being modified by Staff and that you can open a Read-only file or click notify to be told when it is available. Ths is happening in Word and Excel. No one else can have access to these files. This happens sporatically and does not happen all the time to one file.
Files are on a NT4 server with SP 6a