[jQuery] Help with ajaxForm in tabs, file uploads fail with strange error

[jQuery] Help with ajaxForm in tabs, file uploads fail with strange error


Hi, I'm going crazy with file upload ans ajaxform when the file field
is in a tab.
When I click on submit button I got this error in firefox console:
form.submit is not a function
(?)()()jquery.form.js (riga 223)
[Break on this error] form.submit();
I've put a sample page here:
http://lab.gianiaz.com/jquery/file_upload_in_tab/index.php
Thank you in advance.