Jesus guys, I have been using Avast (free version) for over four years and have never had issues with... anything. Best AV for the money (if you pay for it, which I do not).
Having said that, I did have to add CMSF to my exclusion list after Avast quarantined my exe a few months ago. No big deal as it was easily corrected. CMSF is the only program that I have ever had to add as an exclusion in Avast.
Excellent AV.