was when trying to have both it and Netscape on the same PC and being obsessed with downloading every update for each that came along. I had also moved the cache off the primary drive. Mozilla and Netscape do some sharing. Eventually, I had problems..especially when linking from E-mail (I use Eudora). My solution was similar to yours. I blew them both away and installed Firefox...never looked back.
I had the chance to get a dead Mozilla. In short, the fix was:
1. Delete \Program Files\Mozilla.org
2. Delete \Program Files\Common Files\Mozilla.org
3. Install Mozilla.
While successful, maybe someone else can narrow down what it was in particular, but it's running now...
Bob

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