Authentication error when trying to install or uninstall using Ubuntu Software Center (14.04)

when trying to install or uninstall from Ubuntu Software Center (14.04). I'm getting the error message

**Software can't be installed or removed because the authentication service is not available. (org.freedesktop.PolicyKit.Error.Failed: ('system-bus-name', {'name': ':1.85'}): org.debian.apt.install-or-remove-packages** 

when I try to install or uninstall anything from the Center.

I'm running this through Crouton on a Chromebook. Is there anything I can do to fix this issue?

I was faced with the same problem and the following solution fixed my case:

1. check whether you have policykit-1-gnome installed. (I only had policykit-1 installed before). If not, install it using apt-get.

2. run /usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1. Now try to start software center from launcher and software should be able to be installed successfully.

3. add /usr/lib/policykit-1-gnome/polkit-gnome-authentication-agent-1 to your startup applications. press super key and search "startup applications" in all programs. Open it and click "add" to add this command line.

Good luck.