The form works without the File Upload added. Adding it though will result in an endless rotating arrow, never makes it to error/success message and in the console I get:
TypeError: Result of expression '$.handleError' [undefined] is not a function.
jquery.form.js (ver=2.47) line 383
The JS gets loaded at the end of the page. Read the docs, the tutorial, the comments and I triple checked the form setup and tried it with the most simple (no limits) file upload. Always the same problem. The moment I take that one line out, the form works again.