Hair-pulling network problem

Hello

I'm pulling my hair out over this one, I hope someone can help.

We have a database application that runs on a little known 4GL platform
called Build Professional by Today Systems. It used to live on a SCO
Openserver box but we have moved to linux. There were no problems while it
was on the SCO box except that it was painfully slow. The client software
runs on Windows, most of the work is done on the server.

The problem is that clients on the wired network can connect with no
problems but clients on a VPN, ISDN link, Wireless bridge (or presumably
anything other than cat5) either cannot connect, or have to try several
times. My thoughts are that we must be coming up against some sort of
timeout or something. There is no firewall running on the box and it is
pretty much a stock "everything install" of RedHat 7.3. It seems to have no
problems with pings, ssh, remote X sessions, ftp, etc - just this pesky
Buildpro app.

If anyone is prepared to get their teeth into this, I have some ethereal
traces and an error log available...

http://www.sampson.pwp.blueyonder.co...edcon-detailed
http://www.sampson.pwp.blueyonder.co...odcon-detailed
http://www.sampson.pwp.blueyonder.co...ic/smerrHX0FpZ

TIA for any help or hints
Tim