pdf form fields populate sporatically

I have a coldfusion application that populates several dozen fields in a pdf form using the following tags:

<cfpdfform action="populate" source="my.pdf">

    <cfpdfsubform name="P1">
       <cfpdfformparam name="text1" value="test">

       ...
   </cfpdfsubform>

</cfpdfform>

I had all of the fields populating correctly and then something happened and now i only get some of them.  go figure?!  P1 is the form on page 1.  I also have a form on page 2, P2.  I have verified all of the field names, and location, i.e. that they are on the correct subform, but i still only get about half of the fields populating and no error message!

Anyone have any tips for troubleshooting this, apart from using a reeaally big hammer?

Thanks, Alex