This is familiar and happened to us once. I can’t quite recall what the deal was, in part because there had been something odd on that SO which I knew about and figured that it had something to do with that. I know that it was limited to one SO. Even when you opened the record itself to edit something (or just open the record in edit and hit save without making any changes) and then hit save it would give you the same message, even though we clearly weren’t trying to delete anything. It wasn’t the SO itself, but it had to do with something that was linked to it. I think it was a WO or a PO, one that had been tied to the SO, and then something changed. If this is the same thing that happened to us it should only be on 1 record. Once you find that record, go through the line item history look for a line that had a record associated with it and now doesn’t likely through a PN change on the line, or some other change that really sticks out as odd. The “record” the error message was referring to was not really the SO but a line item on the SO. I think that we had to do something on the associated record before we could do anything to SO. It was really strange because it was as if the an error message should have been triggered at some other point but didn’t which then led to this problem.