I'm having a serious problem. I use dual OS, so I'm posting with Windows. Somewhat about 2-3 hours before everything was working fine I have modified Ubuntu a lot and was using Mac OS X login screen. It was working fine but I was just having fun and typed this command in terminal to power off (using Ubuntu 13.10) {and using root}.
sudo shutdown -h now
Also I changed the password for su using
sudo passwd root
I kept my laptop aside and came after 2-3 hours. it booted with a splash screen of mac. then it took to a blank screen (OK this happens every time, but after 5-10 seconds login appears), but these times I'm getting a black screen with a mouse. I can move the mouse but can't log in. Only the black screen is there, but everything else is working when I press power button it shuts down like usual.
I'm stuck, please help me!