still Loading but not success message when form include upload file field

Hello,

WordPress version : 3.5.1
Jquery version : 1.5.2 (manually change in functions.php)
Contact form version : 3.4.1

Only When i put a upload field in a form the js seem to be block and no sucess message appear, and no error message appear when all field are not correctly filled.
But the mail is well send and received with the join file.

Form with no upload field are well redirect with js success message.

Thanks for your help

http://wordpress.org/extend/plugins/contact-form-7/