Id has been logged in already. would u like to log in again?

This particularly happens when your CrossFire doesn't close properly, still leaving your account logged in/connected to the server which generally happens when your game crashes, you force exit the game, and even sometimes it does it randomly.

It's there for security reasons as well - if you haven't given out your information, then you shouldn't be worried, but if you are, perhaps change your password and any other details they may have acquired.