🚀 go-pugleaf

My machine has developed a nasty new affliction.  Every now and then, a
process called "Nubus Receiver #xF0" wakes up and thrashing away without-
interrupts.  The mouse tracks, but nothing else is alive.  The "network"
status light (at least I think that's what it is, the one that's about two
inches to the right of the run light) flickers like mad.

After a while, the lights go away, but the machine is still dead (except
for the mouse).  When I warm boot, the only change is that the mouse stops
tracking, and about a minute later, it crashes (flipped video).  Warm
booting after that crashes again immediately.  The shutdown reasons are 
either "Sequence break not allowed" or "A data mismatch has been located
in the LEFT VIRTUAL MEMORY MAP RAM M-1: Expected Data  M-2: Received Data
M-T: Virtual Address  UPC-1: PC of the original call to ILLOP"

This has happened three times today, and once last week.  It might be
related to heavy consing, but I'm not certain.  I'm running Release 6,
Explorer II ucode 429.  Extended self-tests all pass.  Any ideas?  Is some
piece of hardware on nubus freaking out?  Or do I have a virus? :-)