We upgraded to the full Internet Security 2015 3 days ago, and since then our Firefox browser crashes constantly. It had not ever crashed before. How do we fix this?

Randall, To check if it's actually AVG causing the issue try disabling (https://support.avg.com/SupportArticleView?urlname=How-to-disable-AVG). If so, Try disabling individual components to find the culprit (https://support.avg.com/SupportArticleView?urlname=How-to-disable-individual-AVG-components).
AVG Guru

Randall, To check if it's actually AVG causing the issue try disabling (https://support.avg.com/SupportArticleView?urlname=How-to-disable-AVG). If so, Try disabling individual components to find the culprit (https://support.avg.com/SupportArticleView?urlname=How-to-disable-individual-AVG-components).
AVG Guru