Firefox is easy to install manually if you want to do that. Pretty much all you do is extract the official tar.gz and use it. You can do this as your normal user if you only want it for that user (you would be running it from your home directory). If you want to install it globally you need to simply extract the official tar.gz in /usr/lib and create a symlink at /usr/bin/firefox that points to the firefox binary in /usr/lib. It is also a good idea to create a /usr/lib/firefox symlink that points to your latest firefox (firefox-2.0.0.11 for instance).
Given that firefox-2.0.0.11 didn't crash on you at first I still really wonder if it is your profile configuration (ie extensions, thems, plugins, settings that are used) that is making firefox crash. That may be why it did not crash on you at first; You were using a fresh profile. Perhaps you will have the same effect if you create another fresh profile (firefox -P or firefox -ProfileManager should open up a dialog where you can do this).
Alternative Browsers
**Browsers very similar to official Firefox...(ie they use the same engine, etc)
Swiftfox - basically an optimized firefox build. Select the one for you processor. You can use the same profile for this and for official Firefox.
3.0 builds - this is still a beta
2.0 builds
Seamonkey - basically firefox with mail and web file editing support builtin
http://www.seamonkey-project.org/
**Completely separate projects
Opera
Dillo is also really nice (light and
fast), but I don't think it is being worked on anymore. Therefore, I don't recommend it.
Epiphany is worth checking out as well if you have GNOME libraries.
http://www.gnome.org/projects/epiphany/
My recommendations...
First, try a clean profile with what you have. Does it work fine? If yes, then add your settings, extensions, themes, etc. Does it still work fine? If not then there's your problem.
If it never worked with a clean profile then install swiftfox. If that doesn't work then installing seamonkey would be a waste of time.
If swiftfox doesn't do it for you then either use Opera or Konqueror or if you have GNOME libraries check out Epiphany.