Developer Web Site

Hi,

I have most of an application working OK.
Am able to POST to create a new Contact and associate with a list.
I am find a Contact ID and PUT most changes like FirstName, CompanyName, etc to the correct contact.

What I have not been able to do is to change the EmailAddress of a specific contact from able@acme.net to bill@acme.net

The result of PUTTING bill@acme.net to an id that has able@acme.net is that:
1. the old contact (with able@acme.net) remains and
2. a new contact is created (with bill@acme.net).
3. The new contact only has an emailaddress, (FirstName, LastName are not retained in the Constant Contact UI)

The HTTP Status returned is 204

Is there something different about setting an EmailAddress compared to setting a FirstName or LastName?

Thanks,
Mike