Movie download locks up computer requiring restart

Frequently when I purchase a rental and I am downloading to my Win 8.1 machine, the download freezes. This causes my entire computer to lock up and needing a hard restart to unlock. I am not sure what could be causing this as I can download continuously using Comcast at 30+MBPs for hours using Vudu or other video services to watch from my local PC while traveling. ITunes 12.0.1.26 continually freezes and it takes about 2-3 restarts to download a 4-5gb HD movie. I would appreciate any suggestions.

PS> I have not updated to 12.1 yet. I am waiting for all the "bugs" to be worked out.