I have gotten a lot of feedback about my problems booting my Q700 
into NetBSD 1.4.2.  Many thanks for all your efforts.  I have tried 
multiple kernels (1.4.3, 1.5, -current) all to no avail.  I have 
checked the RAM to the best of my ability (once Allen told me what I 
was doing wrong trying to get at it!); I have 4 4MB stick o' RAM plus 
the soldered-on 4MB on the motherboard for 20MB.

I got one suggestion from another user that had a similar problem 
when his mouse was attached, so this afternoon- that being the one 
suggestion I hadn't tried- I gave it a shot.  Booted right up.  Huh. 
Seems like the mouse is to blame, or at least something in the adb 
path between the CPU and the mouse (I suppose it could be a problem 
in the keyboard's adb path or a problem with the mouse).  Anyone else 
seen this sort of thing?  Does anyone know if it's likely to be all 
mouses (I don't have another one to test right now) or just this one? 
It's an Apple mouse, one of the Mac II era "Apple Desktop Bus 
Mouse"s.  Garden variety platinum colored thing that I pilfered from 
the Classic II sitting in the corner.