This might not ever occur to any of you but I was online this morning and had a really strange thing happen:
The Game Manager (the little bar down the bottom of battle log that show you that youre connecting to a game) would get stuck at "Connecting". I would go into the game window and it would be all black, and just say "loading" over and over again. It never progressed to the map image and wouldnt say "saving" - which is the last step before actually getting yourself into the spawn-in screen.
Nothing I had done to change anything, nothing in the way of notifications. Just one round: working. The next: stuffed.
I manually updated punkbuster from scratch (actually installed the latest version of Pbsetup at the same time) and did the full BF3 update. That let me install a newer version of Game Manager in battlelog and hey presto - problem solved.
The reason Im making the post - a few forum threads on the bf3 blog etc talked about it, but none had a solution. So this was my fix and Im putting it up here for any of us that come across a weirdo problem like not being able to get into the actual game.
Good luck. Hope it doesnt happen to you!