It's the stuff like this that realy pisses my off. Every time I finish connecting, that annoying message about whats new about multiplayer pops up and every time I press X to get to playing the game, it freezes. I have to turn it on and off and try again. However, I've tried again and again now and it still doesn't work.
Though there is no immediate solution to it, there is long workaround.
You will have to delete the game data for uncharted 3 . Then allow the game to update. The whole update is about 550 mb or so...
After this you will be able to play the multiplayer.
BUT you will have to repeat the whole procedure again once u turn off the game.
I really hope we get some 'expert' help on this. Since this is VERY VERY ANNOYING .