Update Manager is reporting this error:
Failed to fetch us.archive.ubuntu.com/ubuntu/pool/main/s/software-center/software-center_5.2.2_all.deb 404 Not Found
I checked and my Internet connection is working fine.
The correct package name is software-center_126.96.36.199_all.deb (three point-twos, not two). The discrepancy is probably because you haven't updated recently and have the no-longer-available older
Press the Check button in Update Manager and then try Install again (thanks @EliahKagan!)
If that doesn't work, try opening the terminal with
Did you try updating the repo?
There is also apt-get clean
I've had a similar error and then I did apt-get update and it was fixed. Hope this helps!