zfs import panic

Hi list,

 After an spontaneous reboot this weekend our backup server is
panic'ing on zfs import. I've the vmcore file but I can't debug this
with kgdb

:/var/crash # more info.3
Dump header from device /dev/ad0s1b
  Architecture: amd64
  Architecture Version: 2
  Dump Length: 103477248B (98 MB)
  Blocksize: 512
  Dumptime: Mon Nov 12 14:56:12 2007
  Hostname:
  Magic: FreeBSD Kernel Dump
  Version String: FreeBSD 7.0-BETA2 #0: Mon Nov 12 11:49:07 BRST 2007
    root_at_:/usr/src/sys/amd64/compile/MANNY.debug
  Panic String: solaris assert: ss == NULL, file:
/usr/src/sys/modules/zfs/../../contrib/opensolaris/uts/common/fs/zfs/space_map.c,
line: 110
  Dump Parity: 2217569595
  Bounds: 3
  Dump Status: good



:/var/crash # kgdb /boot/kernel/kernel vmcore.3
[GDB will not be able to debug user-mode threads:
/usr/lib/libthread_db.so: Undefined symbol "ps_pglobal_lookup"]
GNU gdb 6.1.1 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "amd64-marcel-freebsd".
(no debugging symbols found)...Attempt to extract a component of a
value that is not a structure pointer.
(kgdb)


Someone can give me a hand with that ?

 Best Regards,

Alexandre