PDF function error: "Platform, Locale, and Platform Name must not be null"

I'm trying to read in a pdf form, complete the fields and send it to the user's browser. However I approach it, whenever I use a cfpdf type of tag, I get the error message "Platform, Locale, and Platform Name must not be null".

For example the following flags an error on the cfpdfformparam line:

<cfpdfform action="populate" source="Order Acknowledgement Form4.pdf">
    <cfpdfformparam name="Text1" value="Test Data">
</cfpdfform>

What am I doing wrong?

Using CF9.01 Developer edition. The PDF was created in Acrobat X from a Word file.

The following works and lists the form field, so I'm guessing that it's not a problem with the source file.

<cfpdfform source="Order Acknowledgement Form4.pdf" result="resultStruct" action="read"/>
<cfdump var="#resultStruct#">