When the update goes wrong, exit iTunes, and restart your computer.
If you still see the error, check if there is a new iTunes version available. Open the program, and go to Menu. Click on Check for updates, and download and install the update.
The other thing that may be the reason for the error is the ports. When certain ports are blocked, iTunes cannot communicate with a server. Check for ports 80 and 443, and make sure they are allowed.
Check your modem and router, and if needed, restart them. It may be the solution you have been searching for.
You should try is updating the Antivirus software. If you still see the error, turn off the software completely.