TCPIP Timeout

I have an AS/400 shell program running on 98 boxes at a remote site that has been causing me some serious headaches lately. The application is very sensitive to brief brownouts in communications…which you can tend to get from time to time across an overloaded WAN circuit. When this happens all of my users go down and have to be kicked off the system…this just happened to 5 out of the 6 users 3 times in the last 15 minutes. As a test I upgraded one machine to XP Pro a couple months ago…it has not crashed even once. It’ll cost me a bundle of money to upgrade the OS on these machines and I’d rather not go through the hassles, though I will if I need to.

What I’m looking for is to increase the timeout on the IP stack. Anyone know the registry key I need to play with?