I am facing the same issue on Fedora 18.
Smart Card is working great in console, but when GDM is running, it doesn't turn to the smart card. It just shows your username and then asks for normal Unix password.
When in text mode, smart card is working great.
But when you turn on the "Require smart card", the GDM asks you for unix password and then doesn't log you in. This is about right, because it shouldn't log you in with Unix password, the only way should be the smart card. Still it doesn't know about it and keeps asking you for the Unix password.
In previous versions, the GDM have separated RPM plugin for Smart Card login, but in Fedora 17 and later it should be included in the GDM.
Did you manage to solve this? Any idea how to fix it?