Age of Conquerors and Service Pack 2

Hi all,
Recently my computer was upgraded to Windows XP service pack 2. After this
operation i cant play Multiplayer games with AoC: i enter in the room and in
a game, but during the lauch session, the monitor show the message "Unable to
join game".
The computer is connected with a linksys wag054 dsl router, if i use a
dialup connection i can play without problems.
I shutown the firell of the router and windows firewall, without results.
The router is setted with dmz and port triggering (with ports of DX7 and DX8)
Many ideas?
Thanks