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_5.2.2.2_all.deb (three point-twos, not two). The discrepancy is probably because you haven't updated recently and have the no-longer-available older 5.2.2 version in Update Manager's cache.
Press the Check button in Update Manager and then try Install again (thanks @EliahKagan!)
If that doesn't work, try opening the terminal with Ctrl-Alt-T and then run sudo apt-get update && sudo apt-get upgrade -y. Then close the terminal and try Update Manager again.
