I see that are ppl who can't login in game, still after 4 months. Here is the tested method that it worked for me. Remember, they are still using Gamespy login data. So...
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Create an account on http://www.gamespy.com and an account on https://secure.gamesas.com, using the same email, username and password for both sites.
Now, you must be able to login in game.
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If you have an account on Gamespy and one on gamesas with different login data, on gamesas site, in Edit Profile (I think) you have an option to link the two accounts. I had this too, but after changing the password on gamesas to match on both sites (email and username the same), that option was gone; I think the linking was made automaticaly.

After you try this, please vote to see if it worked.

i am using my gamespy account, which I created for crysis wars