Hi Natty, and :welcomean to ZA! I'm not as technical as some, but it sounds like your game has been archived (saved) in a way that it won't allow you to save games so they can be used again later. I'm not too sure how that could have happened. I've always had the problem of trying to use them again after they've been saved!
I hope I'm wrong on this, but you may have to uninstall the game and reinstall it again. Hopefully someone else might be able to assist you better than I can.
Be sure to introduce yourself to the whole gang by going to our Introductions thread. You'll find that we are a really friendly bunch, especially when our members read our Forum Rules. Please enjoy your time with us!!