Thank you very much, Jim.

It may hard to read the error message even if I make it run in debugging
mode, because it occures very rarely, and when it happenes, that machine
reboots automatically, and then, that neccessary mesage could be hidden
among lots of others...

When I experienced system crush of our CPU server, I tried to find some
other dual Pentium machine for it.   I failed to do it, because there may be
no Pen III dual motherboard in the market, except only of SuperMicro's
Xeon motherbord, which is very very expensive, and beyond my scope
of fund.  (I was told some $1,200~1,300 for that motherboard!!)  So, I had
to choose Pen 4 mother for that server.   This may also be true for most
of Plan 9 users now.  How we can enjoy multi-CPU nature of Plan 9. Alas!

Kenji