Just in case anyone gets this and can't work out what happened. One possible reason is that you've installed the DOOMSDAY patch when you should be installing the ARMAGEDDON patch (ie, you've already have Armageddon, but the patch you installed was if you didn't the Armageddon expansion). Idiots like me need more differentiation in patch numbers (perhaps patch D1.3a for the Doomsday one and A1.2b2 for the Armageddon one).
OK, its a really stupid thing to do, but I do stupid things from time to time. ... And if you're as stupid as me you might get this error!
OK, its a really stupid thing to do, but I do stupid things from time to time. ... And if you're as stupid as me you might get this error!