Well here's the deal. I upgraded a week ago to the ubuntu 12.10 version. Turns out everything was fine until yesterday when my screen started to go black after merely 30/40 seconds.
I went to the bettery/power app. put suspend whe inactive for in don't suspend and show battery never, is a desktop.
Then went to brightness and lock and set the turn screen off when inactive for option in never, and lock the screen in off.
rebooted the computer but still the system keeps going black in a few seconds, and suspends the system in about an hour.
Thanks in advance.