I was playing on my server to test out the snapshot and I noticed that either it's a bug in the coding or the skin servers are messed up. I have found no way to fix this and it's very annoying because you either get a completely white skin or a messed up mob-mixed skin, and never the one you actually have uploaded to minecraft.net.
I have only noticed this on my server so far and not on single player. That's about all of the detail I can give.