After ajax returns, I get TypeError: ctx[0].aoData[this[0]] is undefined

I'm making some progress with RowReorder, and I came across this message. I wondered if you had this error before?
Any suggestions on what to look into?

TypeError: ctx[0].aoData[this[0]] is undefined jquery.dataTables.js:8025:1
<anonymous>
.../media/js/jquery.dataTables.js:8025:1
methodScoping/<
.../media/js/jquery.dataTables.js:7105:16
update
.../media/Editor/js/dataTables.rowReorder.js:539:20
_mouseUp/<
.../media/Editor/js/dataTables.rowReorder.js:574:6

Parameters for the ajax:
action edit
data[3][SEQUENCE_NO] 4
data[5][SEQUENCE_NO] 3
match ITEM_TARGET%20%3D%20'tractor'

Response looked ok:
{"data":[{"SEQUENCE_NO":"3","ITEM_CODE":"5","ITEM_TARGET":"tractor","ITEM_TYPE":"check","ITEM_TEXT":"check trie tread","ITEM_EXTRA":"tread","CHANGED_DATE":"12\/23 19:50","CHANGED_BY":"duncan"},{"SEQUENCE_NO":"4","ITEM_CODE":"3","ITEM_TARGET":"tractor","ITEM_TYPE":"check","ITEM_TEXT":"Check windshield wiper & washer operation","ITEM_EXTRA":"none","CHANGED_DATE":"12\/23 19:50","CHANGED_BY":"duncan"}]}

Debugger info: http://debug.datatables.net/apaniv