I'm working on trying to expand the amount of usable information
reported in these kinds of traps. This one is a system found
error- despite what Chris and others say, I still think the
pc and ra can be interesting - what's the pc and ra correspond
to for this kernel, and what've you got loaded as options on
this box?

Don't go to a lot of effort to gather the info, though- chances
are good (bad) that it is h/w going sour.