I recently upgraded from ubuntu 11.10 to 12.04. If it makes any difference, My system is a dell inspiron 1520. I encounter a problem whenever i shutdown or restart. It kills all running processes (as far as i can tell), but once I get past the shutdown text screen and the screen goes black, my computer doesn't power off. The fans still run and the screen is still on, etc. I have to hold down the power button in order to complety shut down. Does anyone else have this problem? Help would be apreciated.