OS X :: MBP Hangs After Coming Out Of Screensaver

I've got my MBP running the iTunes cover art as the screen saver, and to lock the computer when it goes into the screen saver. Every once and awhile, it'll hang when I try to bring it out of the screen saver to put my password in. The screensaver will be playing, then I wiggle the mouse, and the screen goes black, as it does normally followed by the username/password box.

But that box never shows up, just the cursor and a black screen. It's not every single time either, kinda intermittent. I've had to do a hard power down to get out of it, unfortunately. This doesn't cause any file corruption, does it? Anyway I've now set my firewall to allow incoming SSH connections only from my user, so that at least I can SSH into it from my iPod Touch, should it happen again.