Graph stopped working

Using Hobbit 4.20, had a custom graph working fine.   Copied that graph
definition, and renamed the [subject] and the data names under it.  When I
saved it, not having changed a thing on the original definition, it
disappeared from the page, replaced with the infamous ncv:name-of-graph.

I commented out the new definition and saved hobbitgraph.cfg.  No change.
Deleted new def and saved.  No change.

So . . . umm, ??