I also had a problem with GFWS earlier today, I tabbed out of the game, tabbed in again, got the message "fps insufficent to online play (something)" then I had to restart the game, live wouldn't sign me in and you have to be signed into live for any progress to be saved :/
Also the Dark Souls trainer is realy ruining the PvP experience, if you check the leaderboards in invasions, the guy with the best score looks like this:
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