Pretty well the exacty same thing is happening to me and my friends.
As soon as one of us invites the others to join the pre-game squad, one of us (sometimes a couple of us), are unable to join the game whilst other times one or two from the squad are sometimes able to join. It seems to only happen (the part where '...please check network connection' screen after the 'Joining Server' hangs for about a minute) to whomever is hosting the squad when we try to join either a 'Quick Match' or even choosing a server from the 'Server Browser'.
I even went as far as opening up the port forwards for BF3 and PSN, and still we are all unable to join the same game. This also includes trying to join a game by yourself through the server browser then trying to follow your friend through your friends list by trying to join their session.
Was working fine yesterday... If it's helpful, I'm on PS3.