Help resolving Session Timeouts

I have three workstations running Windows XP (WS1, WS2, and WS3) mapping a drive to a Windows 2003 server through a Linksys Firewall Router. All three workstations are mapping to the share \\sever1\share . When WS1 connects to the mapped drive the session (computer management > shared folders > sessions) points to User: user1 and computer: 192.168.1.1 (router IP address). As soon as WS2 browses it’s mapped drive then the session object changes to User: user2 and computer: 192.168.1.1 (router IP address) and user1 is disconnected. This happens continually with any number of workstations with the same mapped drive. Unfortunately, when the mapped drive is shown as disconnected (red x) programs that rely on this drive no longer function correctly. Does anyone know of a work around for this problem? Thanks in advance for any help provided.