In fact, I believe, what Yodah said is wrong. You need to toggle autodownload OFF. zzzzyavin is our normal map. It's a modded SP map.
When your game starts (mp mode) go to options and toggle autodownload OFF.
Then try accessing our server, which uses dcmod1.2. Your client will load dcmod1.2 (no fear, you don't have to download it). Now that your client has loaded dcmod, you might still not be able to join, because after loading dcmod, for some players the autodownload option is ON again. So if you're unable to join the server after STARTING the game and trying to join ONCE, you might have to turn the autodownload OFF again, even though you have already turned it off.
This fixes it for most players. I don't know a case in which having zzzzyavin in base helped out.