Have you patched to the most recent version of the game?  You can't log onto Ironclad Online (ICO) unless you have the most recent patch.  To patch it, you need to install Impulse (which is kind of like Steam) and register your CD key.  Then when you log onto ICO you also need to register an account.

Or are you fully patched up and having a problem?  What version of the game are you on?  At the bottom right of your screen it should say what version you're on (ie; v1.191, Diplomacy 1.02, etc.)

No, Ironclad online is just the name of the internet multiplayer. You do have to have the most recent update of your version of Sins to play though, and that means updating with impulse.