Q: imovie download keeps failing

That rules out disk space...

The App Store cache may need deleting.

Go to ~/Library/Caches/com.apple.appstore

Move the Cache.db file from the com.apple.appstore folder to the Trash.

Restart your Mac, try re downloading iMovie.

Downloading past purchases from the App Store, iBookstore, and iTunes Store

~ (Tilde) character represents the Home folder.

Having the same problem. App store had several updates including iMovie. All the others downloaded with no problem, but iMovie download keeps failing.

I am having the same problem with several apps. I tried moving the Cache.db file from the com.apple.appstore folder to the Trash.  No help.  I tried restarting.  No help.

Could this be traced to a corrupt Akamai server cache? Does anyone know to choose a different Akamai server?

Your Akamai comment let me to the solution for me. In my case the problem was with an ad blocker I use on my Kerio firewall. It sometimes gets in the way of iOS apps and iTunes Match downloads on iOS. This is the first OS X app that didn't like it.