What is in Mac OS X 10.2.6 that kills Classic Mozilla 1.2.1?

For reasons too lengthy to go into here, I am stuck using Mozilla 1.2.1
via Classic, currently running within Mac OS X 10.2.4

I recently performed a test upgrade  (on an second  hard disk) to  Mac
OS X 10.2.6 and all of my required Classic applications worked fine
EXCEPT Mozilla 1.2.1, which hung upon starting up. 

This is repeatable. I wiped the second disk, cloned my working 10.2.4
disk to it, re-upgraded  to 10.2.6 and the same problem with Mozilla
1.2.1 happened again

Does anyone have a clue as to what is in Mac OS X 10.2.6 that kills
Mozilla 1.2.1?  I'ld like to disable /remove/whatever is causing the
problem, assuming this is possible.

And no, as stated above, I can't switch to an OS X version of Mozilla.
:-(

Hoping someone can help out here ....