object lookup in code sources

I'm running into a really odd problem with using the new object lookup window 
in a code source.  First off, I notice Formulator doesn't have buttons (?), 
so I'm using a text field with name=document.  The TALES expression for this 
field looks like:

string:id='es_silva_document' onclick="reference.getReference(function(path, 
id, title) {document.getElementById('es_silva_document').value = path;}, 
'${request/model/aq_parent/absolute_url}',  'Silva Document', true);return 
true;"

So, this code source works in kupu when adding a fresh code source of this 
type.  When I click on the textfield, the object lookup window opens, I can 
select the object and 'place' the path into my textfield.

However, if I select an existing code source of this type, the onclick does 
not work.  When I click on the field, it only edits the text.

Has anyone experienced this before?  I troubleshooted a bit with venkman, and 
found a few curious things:

1) It appears the code to retrieve the code source form is called twice.
2) If I put a 'debugger;' at the beginning of     
this._continueStartExternalSourceUpdate, clicking continue twice (because it 
is called twice), the onclick does actually work.

Seems like some wierd timing issue going on, but I have no idea where to go 
from here.  The onclick works perfectly in the forms-based editor.

BTW, I'm using Silva-1.4.1 and kupu 1.3.2

Thanks for the help,
Andy