Can I clarify something? Norton 360 is your main antivirus protection but you've also installed McAfee Family Protection - and no other McAfee product (no firewall, real-time scanning, or anything else).
Family Protection - 2012 or 2013 edition?
Firefox - which version?
Check in the list of Firefox extensions and plug-ins for McAfee products. Which ones are there?
1. I've installed no McAfee product other than Family Protection.
2. Not sure about 2012 or 2013. It's version 18.104.22.168, freshly downloaded off the internet. Is there a better way to find out what version? My other Windows 7 machine has version 2.3.027.0. (Perhaps I'll try downloading that version.)
3. Firefox v17.0 -- the latest.
4. No Firefox add-ons, and only 2 extensions (Norton Toolbar and Norton Protection) but they're both disabled.
It's a pretty bare-bones machine at this point.
Hope that helps!