Black ops online wont work!!?

I have tryed going in to a ffa and a tdm and get nothing the game goes in and shows my rank and other people but when the load screen comes up it gos to waiting for other players then after bout 1 min just backs out but everyone else is in the game what do i do?? i have tryed signin in na dout didnt work tryed reseting the game doesnt work!!! plz help!!!!!