Hi-
If the form is not publishing directly to a form library, please check:
(a) Are you a site collection administrator?
(b) Is the Sandbox service running?
You can test both of the above by publishing a sample form, with some simple code. I've attached a sample form that you could use to test.
The other option is (of course) an issue in the form. What does Design Checker say? If you'd like, attach your form template via the Options tab.
As far as the cascading dropdown scenario, I believe that's covered in the PDF guide. Is that working in Preview mode in your form?