Runaway logins, TCP/IP, UNIX SVR4, AT&T 3555

INFORMIX folks, Most of the following probably is not INFORMIX related, but I thought that I would post it here on the chance that someone may have run across a similar problem. My group is having a problem that hopefully someone out there may have come across before, or have some hints on where and/or what to look at. We have some users connecting to our GIS 3555 using TCP/IP via SWS. The users are running two different PC TCP/IP packages; one is by Chameleon, the other by FTP. Once the users log onto the 3555, which is running UNIX SVR4 3.0, the are immediately placed into an INFORMIX application, INFORMIX version 5.02. What happens is that sometimes the users forget to log out off the application. They will simply close their icon on their PC, shut off their machine and go home. Unfortunately, this does not break their communications link with the 3555. The default shell for the users is the Korn Shell, and we've set the TIMEOUT variable in ksh to kill idle users, but this doesn't always work. I suspect that it has something to do with being in the INFORMIX app, but I'm told by others that sometimes users are logged off, and sometimes there are not. The biggest problem occurs when these users then log in again. Apparently, several identical processes will start themselves up at the same time. I logged onto the machine the other day and observed an ID with seven different ttys, running multiple copies of the same 4gl report. I talked to an AT&T/GIS pre-sales tech rep the other day, and he suggested checking some TCP/IP tunables on the UNIX side. I suspect that there is something on the PC TCP/IP side that isn't "right". Something is keeping the TCP/IP connection up, even when the user's PC is shut down. Could there be something wrong with SWS, or the 3555? Thanks. Any info would be greatly appreciated. Lou Avrami ( attmail!lavrami )