I've seen it happens because a file server may keep files open even after all clients closed them to speed up consequent re-opeening.

>I tried to log into a clients system and use a major file exclusive and got access denied.
>All 15 users said they were out of the system and back to their desktops, yet I still got this message.
>There network administrator found one person still to have the file open even though she swears she was
> on her desktop.
>
>Have any of you had this sort of problem? Any insight would be appreciated.
>
>Thanks in advance.
>
>Brad