This just started happening about two weeks ago. I connect to a client site using Microsoft VPN client (pptp). THis has worked for well over a year until two weeks ago. Now when I try and connect I establish a tunnel but cannot access resources on the remote LAN whether by IP address or UNC, hostname, etc. After about 30 to 60 seconds the tunnel disconnects without error or notification. I have this problem on 3 of my office PCs and also if I try this from my server.
Here's where it gets strange - I have two other PCs in my home office that are on the same LAN as my business machines and they CAN establish a VPN tunnel to my customer's office and ping all devices on the remote LAN! They have the same OS (Windows XP Pro SP3) as the machines that are not successful.
Normally I wouldn't care if I couldn't reach their network remotely as I have other means of connecting, but this client has remote users and the same problem I have has happened to one of their remote users. So now I have to figure it out. I'm not sure what other detail I need to provide. I'm wondering if a new Microsoft patch has had some affect or not.
Some things I have tried:
Removing the VPN connection and adding it again
Run a repair on the NIC
firewalls are disabled on all machines
unchecked and removed tcpip from NIC. Reinstalled TCPIP.
Rebooted (of course)