Steam has patched Civ IV BtS with an update that breaks many multiplayer features and causes problem with some font icons in-game. To rectify this, you will have to opt in for the beta version of Civ IV BtS, there is a legacy version of the game that steam don't support that works perfectly just like the original BtS did. In your steam library, right click BtS in the list and open properties, in there you should see a "BETAS" tab. In the "BETAS" there is a dropdown for the betas you would like to opt into; select the "original_release_unsupported - Original Release - ..." from that dropdown. Another thing about steam is that the folder path for BtS can become so long that the deepest folder of C2C will become unreadable in the windows system. To solve this problem, install BtS in a custom location through steam, the original steam install path is not always ideal depending on where steam itself is installed. Edit: If you want to mod the dll (C++) in C2C you may need the beta version to get access to important source files related to the games python implementation that are not replicated inside the C2C source folder. That is, you won't be able to compile a working dll without having the beta version unless you download those source files on your own.