System reboots building mysql51-client with ZFS v28

I am running a fairly recent current with the new ZFS patches:

FreeBSD topaz.predatorlabs.net 9.0-CURRENT FreeBSD 9.0-CURRENT #0
r212312M: Wed Sep  8 02:03:34 PDT 2010
rfarmer_at_topaz.predatorlabs.net:/usr/obj/usr/src/sys/TOPAZ  amd64

When I try to build databases/mysql51-client from ports, the configure
script runs for a while then prints:
WARNING: Adding fix for interrupted reads

Then the system reboots. The kernel doesn't panic or anything - the
screen goes blank for about 5 seconds and the BIOS starts again. I
have WITNESS and all the standard debugging stuff for current, plus
the DUBUG_LOCKS and DEBUG_VFS_LOCKS options recommended in the ZFS
patch posting. Hardware is a Lenovo Thinkpad T61 with a Core 2 Duo,
4GB of RAM, ahci is being used for the hard drive. There is a 1 GB ufs
/boot, everything else is zfs (one drive, no mirroring, no snapshots,
nothing complex).

Port is up to date:
# $FreeBSD: ports/databases/mysql51-client/Makefile,v 1.100 2010/08/25
09:07:27 ale Exp $

Not sure if this is ZFS related or not. What can I do to collect some
useful information here? This can be reproduced reliably.

Thanks,
-- 
Rob Farmer