Error when reordering handpicked items

We have started noticing an error using the drag and drop
functionality to reorder objects in a handpicked rule (tested with
core 6.0.11+).

To recreate the error:

1) select some objects in a handpicked rule
2) use the drag feature to re-order them.
3) Click SAVE, and then the rule should break.

Using debug=1, we can see the error is:

"invalid typename passed or could not be determined"

Jon Low