Atrios clears it up for you here and here.
Valerie Plame's name was not secret. The fact that she was married to Wilson was not secret. The fact that she worked for the CIA was.
And the fact that apparently the National Security Advisor didn't have a need to know about who was recommending Wilson to go to Niger, and why, but she did know that it was at a level in the agency that was apparently classified should tell folks something.