I don't know you're experiencing the same problem, but my problem had to do with setting up the user account information. If I let it convert my old Netscape account, no problem. Any other strategy - lock up on the next start.

What I do is this.
  1. Rename the existing Mozilla directory.
  2. Make a new Mozilla directory
  3. Install the latest Mozilla in the new directory, allowing it to convert my old Netscape account.
  4. Exit from mozilla.
  5. Copy as much of the old mozilla account over the new account as I want, but at least the entire account root. It'll be something like
    F:\\warpzilla\\bin\\Mozilla\\Profiles\\<name>\\<weird_code.slt>. The fact that <wierd_code.slt> is different in the old mozilla doesn't seem to matter at all. I don't bother copying .\\Cache, .\\Mail or .\\News because I don't care about the cache and I don't use Mozilla for mail or news.
  6. Restart Mozilla, and I'm back where I was with the previous one.