solution for 2015 update resulting in high CPU usage
go to the main board announcing the release of 2015, find the download links and select the version you use.
Download, but don't install.
also download the clean uninstall software, but don't run it.
close your browser
restart computer in Safe Mode (in Windows, as the computer begins to boot, press the F8 key and then select Safe Mode)
on your desktop find the clean uninstall program and launch it.
restart your computer in regular mode
now install the 2015 software NOTE: you'll need your license code if you're using something other than a free version.
You'll need to tweak avast a bit as your settings will not be carried over into the new version
Likely you'll get a pop-up when launching the internet to allow the Internet Security from Avast (at least that's the case in Premier)
you should be good to go - at least this worked for me.