Just an update: I have fixed this and your PDFs should work with Preview now. I had accidentally commented out a fairly crucial line of code residing very close to a not so crucial line of code... ugh.
Having said that, Preview is not the best in rendering PDF forms unfortunately...
In case it's useful to you, here's the PDF that it generated: http://files.getdropbox.com/u/2779/pdfamigo.pdf