>I have an i386 running netbsd-4, and it's been crashing ever since I
  >upgraded recently.

  Are you sure that you use this code?

I am pretty sure it was with the code with the frpr_pullup.  If it
happens again I will nuke my OBJDIR and rebuild and reboot again.  I
just installed a freshly built kernel (without cleaning out OBJDIR) this
morning and rebooted.