Maybe it's just me, but a couple of things still aren't clear to me.

1. Have you confirmed that the field is in fact set as updateable (probably, I'm sure)

2. _Which_ field is the problem? costcode.typeid? Is it a primary key? If not, then what is the field that breaks?

3. Do you browse the view and try to make edits and get the error? So you can USE the view okay, but not change the field? Does the error happen when you tab out of the field? Or into it?