That was the only thing that worked...

I totally agree. I tried everything else on this page-- really, EVERYTHING-- and nothing worked permanently. MyStart just seemed to keep coming back. The last straw was that trying to go to about.config SENT ME BACK TO MYSTART. (Sorry about the all-caps)... So if nobody else ever sees this post, at least I got a chance to rant about the evil that is MyStart. I do want to emphasize that for me (and I don't pretend to be an expert) going through the long list of things to do just didn't work. Resetting Firefox to factory settings was the only thing that seemed to help.