we've faced a problem when trying to play UT 2003 in a LAN (8 players).
After a few minutes, we had this error message ("erreur critique" = critical error in english) :

Each time, we changed the computer that was acting as server and each time this computer had this message.
Moreover, one of the computer had this message from the start and could not even play for a second.
I have to precise that I add some new maps and mutators and, to earn some time, I copied each of my modificated folder from my PC and pasted them on the other PC (the folders pasted were : animations, karmadata, maps, sound, music, system, maps, textures)
What strikes me is the following line : "UdpGamespyQuery DB-U. etc..." The problem may be in relation with DB ?:!?!
May someone help us to know what happens, as this message may be a very well known error ? thank you.
(UT installation is patch 2225 + deatball+ team freeze + DE bonus pack + various maps)