GUYS I HAVE THE SOLUTION TO THIS PROBLEM:

So you try logging in with your gamesas account but it doesn't work, it won't let you create a new account becuase your e-mail is already in use with a gamesas account (the oen you are signed in with reading this post).

Click the gamesas link from the game, go to your profile (control panel) on the site and change your password. Relaunch Crysis 2, put in your username and your NEW password, and hazza it works! This worked for me let me know how you get on!

:)

Bumping this incase anyone else wants to see it.

I dont have that problem, but bumping if it really solves.

tried it the first day i got my game and it didn't work
just tried it again, and it still didn't work
i've also tried the "forgot password" method which also did not work

It's worth a try if you can't log into the actual game on first launch, because this is what worked for me. Sorry it didn't work for you Pyro hopefully Crytek doesn't take much longer with the 1st patch.