That was exactly the measures I needed to take.

The drivers and software installed flawlessly and everything worked fine under Windows 8 but after upgrading to 8.1 (with a clean install) and reinstalling everything, IJ Network Scanner Selector EX would not install. I tried installing in clean boot, I tried installing with all shields turned off, etc. the only way it would install is if I uninstalled Avast.

Here’s the thread at Canon, though it was solved in the MS support forums: http://forums.usa.canon.com/t5/Printer-Multifunction-Support/Canon-IJ-Network-Scanner-Selector-EX-not-installing/m-p/48837