Not sure if this has been posted yet, did not see it on the first few pages.
Any cloaked charm or ward, if fizzled, becomes locked in your deck. This means you can cast the same card every turn, over and over. It will not leave your hand unless deleted. This happens no matter what the reason for the fizzle is. It can fizzle naturally in the case of weakness, or fizzle because of a dispel or black mantle etc.
I posted a ticket to Support about this issue a few weeks ago. As of yesterday, it still hadn't been fixed. I've also had this bug happen to a cloaked card after a reshuffle. The only way to get rid of the cloaked spell is to discard it. Otherwise, like Firestarter said, you get an infinite supply of that particular cloaked spell.
Oh well, Firestarter, guess it's just you and me who think this bug is a problem. It's too bad KI doesn't think it is a problem. Or maybe Cloak is meant to become an infinite spell when you fizzle. Who knows? KI likes to keep combat mechanics a secret unto themselves for some reason.