I was using Ubuntu 12.10 for quite a long time. But from a few days back, I am unable to go to the desktop. The Ubuntu is loaded and the login screen is shown. Even after entering the password, the desktop is not loaded, but the same screen is visible and I am unable to click on anything even though I can move the mouse pointer
To solve your problem, press CTLR+ALT+F1, then type your user name and password.
After that, you should type
After the install completes, press CTLR+ALT+F7 to go back to the LightDM login screen, things should be working again.
I hope this solution works.