I managed to get in some further Multia troubleshooting this
morning.

The "other" resistor packs (non-4.7K) appear to be 39-40 Ohm,
and appear to be okay after all.  (I had previously thought
they were bad.)

Hitting E215 (74F623D) with freeze spray works wonders.  I'm guessing
this part doesn't get much cooling due to its location and slowly fries
itself.

Symptoms in my case are that upon powerup, I get the first line
of output, but do not get the 2nd line "testing xxMB of memory"
(paraphrased).  Cool E215 and power cycle and it works for a minute
or two until E215 warms up again.

Now to find some of the 74ABT623 parts that Jack recommended.

-Dave (Why aren't electronics stores open on Sundays, anyway?)