Shared file crisis

I have software that my users are running that is only licensed for one user. Therefore, we have our file permission set to one user and the two users that access this software exit the application each time the other one needs access. My problem isthat after I applied my Y2K patches to our desktop computers my shared files will not let go of a user when she exits the application. She has to log completely off of the network in order for the share to be released and the other user to be able to access the files. This is an Access based application and the files shared is a database. I have checked to make sure that it is not set to exclusive and have checked the ODBC permissions. PLEASE HELP. I am at my wits end.