Downloading update failed. Network connection lost. Check your network connection..."?

This may sound stupid, and I am sorry in advance if it does. Perhaps it is your router. We had four laptops working on one, and everytime the next signed on, it booted off the previous. Turns out, router and all computer's IP addresses were so close, they were interfering. A simple call to change the router address fixed it perfectly. I hope this helped- I have no idea if it is your problem.