I just spent 3 hours in a chat with a norton person in India. We were unable to get the Norton Internet Security to install at first. It kept downloading it and then it would fail the security check and say it was corrupted. I was finally able to copy the file to my laptop on a flash drive after downloading it to another computer on my network. Now the virus definitions have the same issue. Even when I copy them over from another machine, they will not install for the same reason. I ran the sfc /scannow and it said it fixed them, I've rebooted, I've tried everything I can think of to no avail....
It's a windows 8 Toshiba laptop.