After installation without configuring package manager, restart with your live cd. and go to computer>etc>apt>sources.list file. open the file and write down the contents somewhere exactly as you see in the file. Now restart your pc without the live cd and go to the computer>etc>apt>sources.list file and write down the contents as it were in the live cd sources.list file and save. Now package manager will most probably work (worked in my case).
