What operating system and service pack is this and what version of McAfee SecurityCenter do you have?
If McAfee identified files erroneously, check this out: https://community.mcafee.com/thread/2016
See: To send it to the Threat Center outside of Security Center..... onwards.
If they are in the quarantine folder then they have been suspected of malicious activity and the labs need to know if that is a mistake.
As far as "rubbish addons" are concerned I assume you mean SiteAdvisor. Well it's designed to warn against dangerous websites which most people regard as a good safety measure. If you don't want that uninstall it in your browser Tools/Add-Ons or go to Control Panel and remove McAfee Security, it should ask you what components you want to remove.