kernal dump on zfs file system panic?!? "panic: ffs_blkfree freeing free block"

[John H. Nyhuis]

 	About every 5-10 minutes, my freshly installed freeBSD 7.1 stable box 
hangs and begains a kernal dump.  I get the following error message:

dev = twed0s1d, block = 1, fs = /archive
panic: ffs_blkfree freeing free block
cpuid = 1
Uptime = 11m23s
Physical memory: 1011 MB
Dumping 67 MB: 52 36 20 4
Dump complete

/archive has no files in it as it is an empty filesystem.  In fact, it's a 
seperate spindle from the OS disk.

fsck does not resolve the problem:

#> umount /archive
#> fsck -t zfs /dev/twed0s1d

and I've verified that the disks involved don't have bad blocks.  Since the 
machine becomes non-responsive after the dump, I can't access logs or anything 
to see what happened.

Machine is using ASUS P2B-D mainboard (dual 500Mhz PIII Intel), with a 3ware 
7000-2 raid card.  The 3ware has 2 Maxtor 200GB drives in a RAID-1; these would 
normally be mounted as /archive.  The volume is empty (no files).

Google shows lot's of people having similar problems with zfs, but no solutions 
that I have found yet.

Anyone have any ideas?

 	Thanks,

John H. Nyhuis
IT Manager
Dept. of Pediatrics
HS RR541C, Box 356320
University of Washington
Desk: (206)-685-3884
jnyhuis at u.washington.edu