Problem: Unknown Game Detected

make sure your server.cfg file in your main (cod4 dir) has the same rcon password as manu admin.
make sure your logsync = "1",

in your config file for manu make sure logfile is firecting to your games_mp.log properly.

now try it

As zacabbey alerady said: It seems that your rcon doesn't match with the gameserver one's. The error message isn't very exactly. PLease note, that you have to use a rcon-password. An empty string "" isn't allowed.

Also look here (use Google Translation or something else...): http://www.manuadminmod.de/forum/index.php?page=Thread&threadID=1225