I built the new forms  from scratch. The problem  seems to be that I
originally had these items in a separate list, but the client then decided
they wanted a certain set of functionality that was only available (without
pain) if the items were all in one list. This meant that I had to merge
them into a single list, and point the *second* set of custom  forms to the
first list, modify GUIDs, list  ID/name properties, slightly different field
names, etc.

And yes, if I had known then what I know now, I would have STARTED this way
and built the whole thing with content types made up of site columns. You
never can tell with clients.