I was faced with a similar question once:
Can perfection become imperfect?
Another way of looking at it is:
Can the sage become a fool?
Of course not! To choose to become a fool would be foolish, and so a sage would never be foolish enough to make such a foolish decision to begin with, and so the sage cannot become a fool. In the same light, anyone who should make such a decision would obviously not be a sage to begin with, thus still making it impossible fo a sage to become a fool.
The same would apply to perfection, since wisdom would naturally be a part of perfection.
So now as for the question of whether or not God could create a rock he cannot destroy, seeing that he is all-powerful, he therefore cannot create a rock he cannot destry, since that would mean he wasn't all-powerful to begin with. But then seeing that, being God, he must by definition be all-powerful, it would therefore be impossible for him to create anything he couldn't destroy.
Another argument would be that, if he is the Creator, and not the Destroy, why would he create something to be destroyed; he just wouldn't bother creating it to begin with. After all, he's all-wise too, is he not?
I don't know if these are good arguments, but that's my attempt.