AJAX, Data not saved when file is not attached?

Hi guys,

I used these codes below,

        $(document).ready(function() {
        var progressbox     = $('#progressbox');
        var progressbar     = $('#progressbar');
        var statustxt       = $('#statustxt');
        var submitbutton    = $("#SubmitButton");
        var myform          = $("#UploadForm");
        var output          = $("#output");
        var completed       = '0%';

                    beforeSend: function() { //brfore sending form
                        submitbutton.attr('disabled', ''); // disable upload button
                        progressbox.slideDown(); //show progressbar
                        progressbar.width(completed); //initial value 0% of progressbar
                        statustxt.html(completed); //set status text
                        statustxt.css('color','#000'); //initial color of status text
                    uploadProgress: function(event, position, total, percentComplete) { //on progress
                        progressbar.width(percentComplete + '%') //update progressbar percent complete
                        statustxt.html(percentComplete + '%'); //update status text
                                statustxt.css('color','#fff'); //change status text to white after 50%
                    complete: function(response) { // on complete
                        output.html(response.responseText); //update element with received data
                        myform.resetForm();  // reset form
                        submitbutton.removeAttr('disabled'); //enable submit button
                        progressbox.slideUp(); // hide progressbar


The fishy thing about these codes above, Is when I don’t attached a file the data in the form is not saved in the database.
But when there is a file attached it saved.

I tried it on small form like this one below it works, with or without file attached.

But on a longer form it doesn’t work without a file attached.

What could be the culprit?
Any advice please.

Thanks in advanced.