Access 97 Data or Networkconnection lost

We have on a Citrix-Metaframe 1.9 a access 97 programm runnig which is our main progamm to keep our firm data. Now, when one user is closing down his client all other users currently running this access-programm receve the message: data- or network error. The programm has to be closed and started again to continue work. What can be the problem? Who has an idea?