As Falkyrn has pointed out u are trying to connect to a server that has a custom map installed on its server. The game should just throw you out to the menu screen.
You should be able to download maps from the clan website of the server you are trying to connect to. Alternatively you could try these links click here click here
These maps will be in the form of .pk files and just need to be pasted into the 'main' folder within EAGAMES/mohaa/main. You will then find them on list of maps within the multiplayer section if you go and try to create your own game.
You can get lots of other things like sound mods, blood mods, and skins etc. Hope this helps some.