A couple of other thoughts. Try using Adobe [Acrobat|http://www.adobe.com/support/downloads/product.jsp?platform=macintosh& product=10] instead of Preview, it often works on filling out forms when Preview doesn't. Also there is a pretty cool Mac program called [PDFPen|http://www.smileonmymac.com/PDFpen/index.html]. Finally you could "Print" your PDF to a PDF using whatever application you want, including Preview (in the Print dialog, click on PDF, and then select Save As PDF...), I've also had success editing PDF's that I printed from PDF's that I couldn't edit otherwise.
Just trying to help.
Andrew