zfs+smb checksum errors

[Scott Johnson]

I've been running FBSD 8.0-rel and now 8.1-rel for 6 months or so, with a 4 disk 
raidz, weekly scrubs. Never saw a checksum error until last week when I got 
about 5 during operation, followed by another 10 or so on the next scrub.

They all occurred when I was accessing the server through SMB from my WinXP 
desktop. I've been doing this for months, transferring files to and from 
regularly, but this was the first time I'd been doing simultaneous heavy reading 
& writing.

I was running Imgburn on WinXP, creating an iso file from folders. Both source 
files and destination iso file were on the same SMB share on the FBSD server.

After all the checksum errors, there was 1 unrecoverable error, on one of the 
destination iso files.

There are 0 read errors, 0 write errors, and 0 new SMART errors on the 4 disks. 
The checksum errors were spread roughly equally across the 4 disks. All of which 
leads me to believe this is a software problem at the filesystem level.

What is my next move for diagnosing and eventually resolving this?