Error while setting up any application from Ubuntu Software Center

Hello experts,
When I attempt to set up any application from Ubuntu Software Center, I get the following error message.
"Failed to download package files. Check your Internet connection."
At the same time, when I attempt from terminal, then it seems fine..!
Also, I have no problem with my internet and it seems very good. Then I tried these things:
Apt-get removes software-centre
Apt-get installs software-centre
Apt-get installs updates
Apt-get installs upgrades
All these of no use!
Help me to solve it please.
Thanks.
