I had this exact same problem. When I opened our problematic PDF,
then selected File > Properties, I noticed that the PDF Producer field
said Mac OS X 10.6.2 Quartz PDFContext. To me, this indicated that
the form was filled in using an application that was not Adobe Reader
or Adobe Acrobat and that that other application (presumably Apple
Preview) might write the form data to the file in a different-enough
manner as to cause the problem observed.
Using Bill @ VT's comments (from the same thread), I was able to print
the data only by selecting "Form fields only" in the Comments and
Forms picklist in the Print dialog.
A tedious way to fix this problem might be to use Adobe Reader or
Adobe Acrobat to open the problematic document side-by-side with a
new, empty form, then copy/paste the entries from one to the other.
Alternately, you could ask the form completer to do the same, taking
care to use Adobe Reader or Adobe Acrobat rather than another PDF
application.