this bug (or at least one with an identical callback tree) is still
around in 1.6.1.  I have had three different machines over the last two
days fall victim to it.

all three machines are running identical GENERIC kernels:

NetBSD lauri 1.6.1 NetBSD 1.6.1 (GENERIC) #0: Tue Apr  8 12:05:52 UTC 2003     autobuild@tgm.daemon.org:/autobuild/netbsd-1-6/i386/OBJ/autobuild/netbsd-1-6/src/sys/arch/i386/compile/GENERIC i386 

I didn't know I was able to dig around into vnodes from ddb, so next
time this happens hopefully I can provide a little more information.

What would be necessary to make Artem's extra sanity checks machine-
independent?