Minecraft wiki entry for Saved_data_Dropbox_guide, associated text: If you use third-party mods to the game, you must install all desired mods only once, and then synchronize the patched result. In the unlikely (but possible) case that you run into problems, you should NOT share the bin folder (with its natives subfolder) anymore. Mods known to work cross-platform seamlessly include Zombe's modpack, Mine Little Pony, and MCPatcher.