I think it's what Psyke said: there are certain levels of power that Naruto can reach when using Kyubi's powers. Take the 1st time he drew the power. He lost complete control of himself and was going for the kill only against Haku. Then there's the one where he wasn't as powerful, but good enough to stop Orochimaru's snake. Now here, I dunno what the hell he was doing, but it was utter crap.