Form text fields are disappearing during a merge to new document.

We would like to create a form that has some merged information on it, as
well as check boxes, dropdowns and form text fields. After the merge to a
new document, we would save it as a template and turn on document protection
with a password. The recipient could then fill in the form, using the check
boxes, drop-downs and text fields. However, when I merge the document, the
form text fields disappear, whereas the check boxes and dropsowns don't. How
can I make the form text fields survive the merge? We are at Word 2003 SP1.