I recently updated my laptop from 12.04 to 12.10. And now, whenever I lock screen with "CTRL+ALT+L", the screen locks, and monitor turns off. But within 30 seconds, it turns on and asks for password. After some time, it says 'Time expired' and turns off. This keeps happening until my battery goes dead. :-1

Please assist me with this.

Also, I'm using Dell Inspiron 15R (5520) (no external graphics card). Often the fan speed goes very high for sometime. If you have any solution, please help me. Thanks.