Firefox crashes continually

I'm a newbie user, fresh from a Windows environment for many years. I've had Zorin installed for about four days and am gamely climbing a steep learning curve.

This morning, within an hour after the software update, Firefox began to crash within a few seconds after opening. I uninstalled and reinstalled Firefox with no improvement. Did a complete removal with Synaptic, restarted the OS, reinstalled Firefox. Same problem. Firefox reports that the last session crashed and crashes again usually before I can select to restore or not. I have been able to act quickly and select to either restore last good session or no restore, but still get the crash. FF simply closes with no indication. As a newbie, I don't know where to go from here and need some advice. Chrome still works, BTW (I'm using it now).

I added the Mozilla PPA to the synaptic manager and installed FF from there (Mozilla's site gives instructions on how to do this if you dig around)... I needed it to be the same version (4.01) that I had on OS4 as I have a full backup of my user profile and I did not want to go through the hassle of re-bookmarking and re-installing all of my plugins... The latest FF works without issue on ZOS5