You've never prepared any spells? So it's not that you've been questing, and you have two spells existing from the same rune combo? Or that you've prepared too many spells and you need to forget some? That is pretty odd. This may be a silly question, but... you have been making sure to put the three spell runes in with the exact order, right? It does make a difference. Beyond that, I couldn't imagine what is going wrong.