sudo apt-get upgrade -d

If your update manager is not working and a new LTS version of Ubuntu is out there. Follow this method as I always does.
Hit Alt+F2 and in the run box type

sudo gedit /etc/apt/sources.list

Now replace 'karmic' with 'lucid'. Save the file and now write in terminal

sudo apt-get update

and then

sudo apt-get upgrade -d

Put your computer on a scheduled shut down and sleep. As I always does. :-)