A NEW AVATAR ?
I have had this problem for a few months. Black screen with the Oh, no! message at each boot.
Being fed up, I installed and used XFCE4: no problem.
Then I noticed: following login, XFCE4 immediately issues a prompt for the SSH-key passphrase. This is a wanted feature programmed in my .profile inherited from Scientific Linux since my first Fedora 10!
Fedora 16 + Gnome 3 used to prompt as well and I used it in my office. But I got sick and did not need keyed SSH in the hospital nor now at home ... and I failed to notice the disappearance of the passphrase prompt under Gnome!
Trivially SOLVED by yum install x11-ssh-askpass
This explicitly OpenSSH functionality has obviously diappeared from the OpenSSH package.
More generally, when getting the "Oh, no!", better check human memories for a missing prompt or message expected during login!