One more thing... Mtgox states that the address is valid for 24hours. What happens if it takes longer than 24hours to be sent?
Oh, then you might have a problem. I don't know what does that mean, I hope MtGox won't simply delete the keys.... maybe they will delete the association of that address to your account, but then it can be recreated manually. (what's the point in making a deposit address temporary?)
I would contact them.