OnAfterChange not working

[foomonkey]

I have an InfoPath form that is the basis for two different Sharepoint
forms libraries. I have "Published" the form to each library. The form
has an event handler (OnAfterChange) setup on one of the fields.

If I create a document in the first library, the event handler fires
correctly. If I create a document in the second library, the event
handler fires correctly. If I create a document in the first library
and move that document to the second library, the event handler does
not fire.

I have updated the processing instruction in the XML instance document
before moving the file and it still does not work.

Any ideas why the event handler does not fire in this instance?

Thanks.
Andrew