I have tried to get help from Mozilla and they suggested Microsoft help. Here is the link of what has transpired with Mozilla Help thus far. I have been working to fix this problem since 7/13/17.
This all happened after the last Microsoft Update on 7/13/17
Firefox is running in Task Manager even though Firefox window never opened after launch.
I have a Compaq with XP SP3, Firefox 49.0.1 and tried 52.0.2, AVG Security, Malwarebytes, SuperAntiSpyware & SpywareBlaster. The only browser I have that works now is Google Chrome.
I have uninstalled Microsoft Security Essentials because of the errors 0x80070002 and 0x8004FF52
I have uninstalled Firefox but can't download a new version. IE will launch, window will open, but nothing loads.