Ubuntu x11 problems

Ubuntu had gone into screen saver mode. I moved my mouse, but instead of ending the screen saver, the screen saver froze. However, I could see my mouse pointer, and move it around. There was no response to any keyboard or mouse input, so I did a hard restart.

When the login screen came up, I tried my username and password. I accidentally put in the wrong password and the screen froze, so I tried CTRL + ALT + BACKSPACE. Now I have a screen that says:

The greeter application appears to be crashing. Attempting to use a different one.

I pushed ok a few times and finally it got out.