I had this exact problem yesterday, with Fed13 running in VMWare. These details aren't important. I was groaning at the thought it had something to do with X drivers or a bad kernel. Ugh! Luckily that wasn't the case.
Turned out to be the lack of a login manager (or whatever it's called these days) - gdm, kdm, or something to bring up a regular login prompt. Somehow during a session of massive upgrades and removal of unneeded packages, I removed gdm.
Solution: Alt-F2 (or other Fn) gave me a normal login, so I logged in as root, ran yum install kdm (or pick your favorite) and after that all was normal.