Hey,
since my internet connection has been upgraded (50 mbits download) I've been encountering some serious issues with Avast.
When I download bigger files, usually >200MB, Avast will often start to use 30-50% CPU, slowing down my PC significantly, and will also completely bog down my internet connection so much that Firefox fails to load webpages and the download just stops midway. The only solution I've found so far is to disable it completely while downloading anything which of course isn't exactly what I like to do.
I've already tried restarting my PC and even reinstalling Avast from scratch, nothing changed.
Avast Version number is 2015.10.0.2208
I'm using Windows 7 32bit, Intel Core2Duo E6750 2.66GHz, 2GB RAM