[ubuntu] Ubuntu 12.04 unable to install through software centre

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http://ubuntuforums.org – Hi I have installed Ubuntu 12.04 LTS and updated using a mobile broadband. But whenever I use another wireless network to do this it does not help. I can download .deb file and install through ubuntu software centre while using the wireless network. But I cannot install through the ubuntu software centre directly. What to do? Please help me... (Hardware)