MS Access sharing problem

I have a MS Access database in 2003 server (LAN).I have shared the folder where Database resides and given proper permissions to each user(Active directory).I have mapped this drive to all the work group computers by appropriate username and passwords (managed by the server where the database exists).I have created shortcut from this mapped drive to all clients.I can’t access the database simultaneously.If one computer opens the database others can’t open.Can you please guide me?But if I open MS Access seperate and opening thru open dialogue box, it opens.Thanks in advance