If you could post shots of your equipment and gear it would be easier to explain but anyway the attribute points shown on the avatar screen are cumulative, including equipment boosts. So when you tried to change robes and couldn't, you wound up with no robe on. In that state, I am guessing you no longer had the Int to wear the other gear, which causes it to be automatically unequipped. I don't know what you mean about level 24 but there are no level 24 tiaras. At least post your stats and the stats of your gear so people can better understand what your problem is exactly.