I rarely have panic on my NetBSD/sparc's and infact with the exception
   of my cdrom panics this is probably the first:
   
   Oct 16 20:43:03 NetBSD savecore: reboot after panic: pmap_page_protect !PG_V

there's a pr from me about this.  i get it fairly regularly and always
with the same steps leading up to it:

reboot machine.
<maybe play a bit as root on console>
login as me.
<maybe play a bit as me on console>
run X.
<maybe play a bit in an xterm>
run screen.
BOOM.

the maybe's don't need to be there, but, they don't stop anything...

so, it's the, reboot, login, run X, run screen, boom sequence that
does it.

i don't know what it is.