Game "Ultima Online" crashes WinGate Server

[Havenard]

I have a Windows XP Professional full updated with a WinGate 5.2 Server installed. When some of the clients is running Ultima Online (Game), sometimes, fortuitously, the server lost all the connectivity with the Internet, and with the Intranet too! The server don't show any error message, but cannot see the local sharing machines and cannot connect to any website in the Internet. My only exit is to restart the machine.
By client-side, nothing happens too except a "Connection Lost" message in the game (Ultima Online).
The only special configuration of my WinGate Server, is the HTTP Proxy port changed to 180 (because I have IIS on 80). But I think it's not the cause of the problem.
I can't figure out what is happening, but I believe the problem is some bug in the WinGate (buffer overflow?).

Thanks a lot for who can help me with this problam.
If it's realy a bug, I would like that the support team send me a patch or some solution by e-mail.

Thanks all (and sorry for my bad english).