We were talking about Modular XML Loading in this thread recently. For some reason you have to set ModularLoading = 1 first in the Civilization4.ini file to use mods using the new modular XML approach introduced by Beyond the Sword. There is consensus that this is major inconvenience many people will probably stumble over. As far as it is known, there is no drawback to an activation of this parameter. So please set it to active by default.