Having the files won't help you. You have to set Autodownload to off.
If you still experience problems, it might be for this reason:
when you start up your game, you start a unmodded version. But we use the dcmod1.2. Once you try to enter a server with a mod, your game loads that mod. Your settings in the mod may differ from your default settings.
So, when you start up the game, put the autodownload to off. Try to join the server. If it still doesn't work, check your settings right again, and put the autodownload to off again. Then try to join the server.
If this doesn't help... <.<