Ah if it's game joining then it's not a version mismatch (to log on ICO you need the latest version and that's the only version that works). It's a data mismatch. Either you or the host has modded files in the main directory or a mod enabled, and since it sounds like you're having issues joining any game, it's likely you. If you're certain you don't have anything modded and aren't running one, your best bet would be to uninstall, manually delete the installation path, and re-install.
