I've just installed Norton on my Lenovo Yoga running under Windows 8.1. Before that Avast was installed and caused me no problem at all. I've had to disable Norton's firewall, otherwise I couldn't go on the Internet. I read on this forum that I must re-initialize the firewall, which I did... and which sent my machine in an endless and frightening reboot session. I switched it off, then comes the reboot screen again... Windows finally launched, and now it works and the firewall doesn't block my surfing anymore. Hope it is for good:/
Edit: Still working, and Internet speed is notably faster than with Avast!