Install button in Software Center is disabled [closed]

For some unknown reasons Install button is disabled in Software Center and therefore I am unable to install any software from Software Center. But it is possible to install software using command apt-get install package_name.

I have Internet connection through 3G modem but I think Software Center doesn't have internet because it shows a notification saying 'No network connection' (Sin conexión de red).

In the screenshot below you can see the problem I have described:

EDIT 1

When I run it from terminal with software-center command it outputs following messages:

2011-12-28 22:31:30,618 - softwarecenter.ui.gtk3.em - INFO - EM's: 17 15 21
2011-12-28 22:31:31,028 - softwarecenter.backend.reviews - WARNING - Could not get usefulness from server, no username in config file
2011-12-28 22:31:31,102 - softwarecenter.ui.gtk3.utils - INFO - Softwarecenter style provider for ambiance Gtk theme: /usr/share/software-center/ui/gtk3/css/softwarecenter.css
2011-12-28 22:31:32,513 - softwarecenter.ui.gtk3.app - INFO - software-center-agent finished with status 0

I've also had csome problems. Re-installing software center can't fix it.

You have an alternate solution. Just look at the top left of this picture http://i.stack.imgur.com/YrBy5.png and you will get it.

You can't click the install button because it seems inactive/disabled, so just go to the top left and find file -> install. I hope this will help you.