at second submit, the upload file disapear, and the user register without picture

I have put on user register form some profile fields. And if the user gets an error message from validation, the user picture disapears, and the user is registered without picture!

I fixed the problem.
In the module script you must change the 'validate' case to handle if not exist picture:

    case 'validate':
        // validate uploaded picture, taken from user module
        $validators = array(
          'file_validate_is_image' => array(),
          'file_validate_image_resolution' => array(variable_get('user_picture_dimensions', '85x85')),
          'file_validate_size' => array(variable_get('user_picture_file_size', '30') * 1024),
        );

        $file = file_save_upload('picture_upload_register', $validators);
		if (!$file){form_set_error('reg_with_pic','No picture!!!');}
        break;