Every time I open my Firefox browser, I get my homepage AND Add-ons Manager (or sometimes only Add-ons Manager). When I go there, it says there's an update for Microsoft NET Assistant Framework 1.3.1. When I try to install it, it never finishes installing. I've left it for hours and it still never finishes (it actually barely starts). I've disabled automatic updating but it does this, anyway. It also opens a new tab for Add-ons Manager every time I open a new window. PLUS, every time I either open the browser or open a window and Add-ons Manager opens, it AUTOMATICALLY goes to it, which messes up whatever I'm doing. I'm currently using version 16.0 (and 15.0 - can't use only one). What can I do to stop it from opening and checking for this update?