Possible Duplicate:
How to fix 'Check your Internet connection' error in software center?
I am using Ubuntu 11.10 . I have a problem with the Software Center. I am not able to install anything from it. After I entered my authorisation password it gives the following error:
Failed to download package files check your internet connection.
After that it says
Requires installation of untrusted packages. The action would require the installation of packages from not authenticated sources.
Firstly make sure your internet connection is working. Can you browse websites in your browser when this error occurs?
You might need to update the package metadata. Close Software Center. Open the Unity Dash (top icon in the dock) and type "Update Manager". Open the Update Manager, and click on "Check". Wait for it to finish (this needs an internet connection), close it, open Software Center, and try to install. Note that installing the updates suggested by Update Manager is not necessary for this (but is recommended in general).
Alternatively, instead of the Update Manager you could also do
sudo apt-get update
in a terminal.Open the Update Manager, click the Settings... button, and check Source Code under the Ubuntu Software tab. Then, back in the main Update Manager window click Install Updates. (source)
If it doesn't work then can you post the output of
cat /etc/apt/sources.list
and thengpg --list-keys
from the terminal?