I just bought Crysis Warhead through Steam and when trying to play a multiplayer game for the first time (of Crysis Wars), I got the infamous "CD Key is invalid, would you like to edit it?" error.
After some research on our dear friend Google, I found that other users had the same issue and had a new key provided to them by EA by calling their number (+1-866-543-5435, option 9).
Don't use Live Chat support... See this thread for the source: http://forums.steampowered.com/forums/showthread.php?p=19907617#post19907617.
So I called them and explained my situation to the support agent (Aaron S.). He asked me for my EA Account information (you must have one, if not create an account
here), and then the invalid CD Key. He confirmed the key was indeed invalid and gave me a new one to try. I had Crysis Wars opened in the background so I immediately changed the key and was able to connect to a game afterwards.
Then I told him I wanted a permanent solution because Steam will keep an invalid key if I have to reinstall the game again, and I didn't want to edit registry values or stuff like that to make the new key permanent in the Steam install. That's when he told me he could add the game (with the new working key pre-entered) to the
EA Downloader account associated with my EA Account.
I then had to refresh my games in the EA Downloader and saw the new Crysis Warhead game showing "Ready to play" below it. I had to uninstall the game I installed with Steam (using the "Delete Local Content" right-click option) and then refresh again to see "Ready to Download". To refresh the EA Downloader, use the gear icon in the upper right and select Refresh My Games.
The game is re-downloading now, but I'm confident it's gonna work. I just find it damn sad that Steam has a bunch of invalid keys and think they should address that issue on their side!
So if anyone has that problem, here's the WORKING solution!