I'm running 8.0.3 NE. When I go to the Tool and Migration->Backups page, I get the following error:

Server error encountered
Message: unknown document: BackupQueryRequest Error code: service.UNKNOWN_DOCUMENT Method: [unknown] Details:soap:Sender
and no backups are shown.

At the command prompt:

zimbra@mail:~$ zmbackupquery 
Label:   full-20130724.223002.883
Created: Wed, 2013/07/24 17:30:02.883 CDT

Label:   incr-20130720.223009.535
Created: Sat, 2013/07/20 17:30:09.535 CDT

Label:   incr-20130722.223007.463
Created: Mon, 2013/07/22 17:30:07.463 CDT

Label:   full-20130719.223008.375
Created: Fri, 2013/07/19 17:30:08.375 CDT

Label:   full-20130720.142144.356
Created: Sat, 2013/07/20 09:21:44.356 CDT

Label:   incr-20130721.223008.235
Created: Sun, 2013/07/21 17:30:08.235 CDT
Yesterday's backup show okay.

I also stopped receiving the backup success/failure emails yesterday.

Now to tell you what I did...

I had a failing disk, so I moved the data to a new disk with the following command:

rsync -avHS --exclude backup /opt/ /opt1/
I then changed fstab to mount /opt1 as /opt and reboot. Zimbra came up and ran fine. Then I ran:

rsync -avHS /opt1/zimbra/backup/ /opt/zimbra/backup/
to get the backups over

Any idea as to what's going on here?