Agent update may fail. If you go to the install files you may find a little lock picture on them and if you try to delete it, it will say windows defender has a lock on it.
this is a windows issue and that you need to authorize our software in windows defender.
see attached screenshot.
This potentially could come in to play with windows xp and up, it is a add-on product that anyone can install.
http://windows.microsoft.com/en-US/windows-vista/Add-or-remove-items-from-the-Windows-Defender-allowed-list
