Hey there,

It's really strange, when i try to join a cooperative game in my LAN, it conects but i get stuck in the console.

Is there any console command to start playing?

Did you try to use a new engine? is a good choice for multiplayer. But check the list [url=http://www.quakewiki.net/quake-1-engines/]of engines.

Personally I do the coop Lan parties with Darkplaces and Small Mod Compilation with personal settings that disable everything that works badly in MP.