VPN Connectivity seems to time out after 3-4 min

[rmcar]

We are using W2K server for routing and remote access. We have some users(using XP SP2) who are able to VPN using PPTP and access Our Network resources without a hitch, the connection stays up even when there is no activity for as long as needed. Other users(using XP SP2 also), particularly when connecting through a wireless access pt(although it also happens to hardwired connections too), seem to time out after 3 to 4 minutes. I have not been able to find any settings or event viewer clues as to why this is happening. We have tried adjusting the MTU settings and haven't had any luck.
Any ideas? Thanks

 

[msworld]

If you have modified the MTU, you may want to upgrade the wireless router firmware. This search result may help,

VPN connection is disconnected after several minutes
VPN connection is disconnected after several minutes. We have been seeing more and more cases like this one. We don’t really know the causes, ...

http://www.chicagotech.net/VPN/vpn3minutes.htm

Bob Lin, MS-MVP, MCSE & CNE
How to Setup Windows, Network, VPN & Remote Access on

http://www.HowToNetworking.com