ITunes glitch trying to download ios 8 for iphone 5s?

Once i click update on iTunes, the software update timer in the top of iTunes just keeps increasing by 2 hours for every second that passes. So after about a minute it says 120 hours remaining. It just keeps increasing until I click manually stop the update.
How do I fix this?

This article summarizes the most commonly encountered problems or issues that you may meet during or after updating to iOS 8 with the corresponding solutions.http://www.imobie.com/support/common-ios-8-upgrade-problems-and-solutions.htm