I took Matt's suggestion of PR_PURGEIF flag, and purged only those
protocols.  A kernel with this change survives removing a card, and
I'll get this installed on my troublesome ppp systems and see how they
behave (the crash was not 100% reliable).

Patch is at:

http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=29580

-- 
        Greg Troxel <gdt@ir.bbn.com>