Had a brilliant thought (which are becoming more and more elusive these days.)
Last year I was playing with cheap Arduino clones which use the CH340 series USB chips, and
of course, had to download the Chinese USB driver to match. So, just now I reinstalled the
FTDI drivers and (drumroll please)... Success. No more kernel panic.
I will attempt to mark this as Solved, but if not successful perhaps a kind reader will do so for me.
Thanks for the responses - especially the one that suggested a bad driver.