ZFS scrub gone wrong

Hi,

Tonight I was manually running a scrub on my ZFS pool for the first 
time. After a few minutes of operation, sound began repeating and the 
computer spontaneously rebooted.

All I have in the logs is:

*Jun 20 22:31:46 nexus root: ZFS: checksum mismatch, zpool=mypool 
path=/dev/ad1s2 offset=47253578752 size=3072*
Jun 20 22:32:53 nexus syslogd: kernel boot file is /boot/kernel/kernel
Jun 20 22:32:53 nexus kernel: Copyright (c) 1992-2007 The FreeBSD Project.
Jun 20 22:32:53 nexus kernel: Copyright (c) 1979, 1980, 1983, 1986, 
1988, 1989, 1991, 1992, 1993, 1994
Jun 20 22:32:53 nexus kernel: The Regents of the University of 
California. All rights reserved.
Jun 20 22:32:53 nexus kernel: FreeBSD is a registered trademark of The 
FreeBSD Foundation.
Jun 20 22:32:53 nexus kernel: FreeBSD 7.0-CURRENT #3: Sun Jun 10 
12:43:23 WEST 2007


The pool:

  pool: mypool
 state: ONLINE
 scrub: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        mypool      ONLINE       0     0     0
          mirror    ONLINE       0     0     0
            ad0s2   ONLINE       0     0     0
            ad1s2   ONLINE       0     0     0

errors: No known data errors



I'm not sure if it was a coincidence or not, but it crashed while I was 
doing a zpool iostat 1.


Any ideas about the ZFS error shown above ?

Best regards,

Hugo