NT Shows open files when they are not!

When some users start a foxpro multiuser program, foxpro reports that a certain file is in use and won’t let the user in. The file in question opens and closes almost instantly in the foxpro app when the program is started. NT reports that the fileis open by a certain user. I’ve had all users log out and shut down and NT still shows that the file is open. Under server in control panel, you can close resource and it works. Refresh doesn’t close the file. Is this a cache thing or what? How often is this info refreshed? NT4 server service pack 4. Thanks.