Server 2003 Cannot connect to some clients

We have MS Server 2003 and recently it became unable to connect to just 2 of the systems on the network. They all have had thier documnets folder mapped to network drives. When you try to connect to either of the two system as a network place for example it shows the system but none of the shared folders on that system. When I try to connect by typing either the IP of the system or the system names in the run box it says that the network path is not found. When I try to ping the ssytem it pings an address that is incorrect for the systems and times out. System IP = 192.168.1.123 but Server pings 192.168.1.184. I have tried to change the system's IP to match what the server is pinging but with no luck. When I try to ping the system by IP it times out 4 times. It really sounds like a connectivity problem but both systems can see, connect and use the server just fine. Other systems on the network can connect to the ones that the server is having issues with. The only thing that the two systems have in common is they has been testing VPN connections to the server with them recently.