Cannor Create Server error message...

[Swissy]

Help!!

I just got HD2 and SS... and when I go to create a server for some friends to join, I get the error message "Cannot Create Server - press ESC to continue" - happens both in LAN mode and Internet.

I have 1.12 patch for SS loaded
Ports forwarded (and tried full DMZ mode)
Firewall exceptions added (tried deactivating software firewall)
Allowed access in Antivirus (deactivated AV as well)

I can see and join other online servers, but cannot create my own. I have added the extra Co-Op maps and edited to maplist file...

Full version of the game with issued CD Key.

Tried a dedicated server and after the console said "game running" it shut down and tried restarting multiple times but gave a message that 'could not open file dserver_11001.txt'

Ideas?

[Swissy]

ok... here's an update. If I bypass the router and hook my computer directly to the cable modem I can host a game. When I do this, norton Antivirus 2005 comes up with it's warning asking if I want to allow the game to access the net. Selecting yes allows the game to create the server.

Hooking the router back up, setting the router (Linksys WRT54G, 3.03 bios) to DMZ and turing off M$ Firewall still makes me unable to create a server.

Even using Port Magic to manage the port forwarding will not work. I'm emailing with the linksys support but if anyone has any pointers I'd REALLY like to hear them... I'd prefer not to bypass the router to play...