Start firefox from the command line and look at the error message when
it dies. That message ought to be informative and will most likely zero
in on the cause of the trouble.

I would guess you have a lock file in the .mozilla directory.
Open a terminal cd .mozilla/firefox. Once in there ls and then
cd to the whatever.default. Once in there ls again, if there is a
lock file rm lock and hopefully everything will work.

"Bus error"

That's the only line/message it gives.

bus error - that means the application (firefox) tried to access
memory which was physically unreachable. I've heard of one user who
fixed this error by removing and re-installing xulrunner. Another one
solved it by removing and re-installing flash and java. Yet another
solved it by removing firefox, xulrunner and nsplugin, and reinstalling.

Open System Monitor and check that there is not a copy running in memory.
Just scroll the list of applications and if you see Firefox, kill it.

I forgot to mention that I did check system monitor while starting
Firefox. It came and went as quickly as the app. leaving nothing in the system
monitor.

After fiddling with some un-installs and re-installs with no change, I
re-installed KUBUNTU. Problem has been solved. /Home is on a different drive so
no loss there.