This code works in FF and chrome. In IE 8 or 9 I get a 500 error saying a not null property is null.

Here is the html

<div id=upload_button_div_general class=fileupload-buttonbar data-url=/Upload/SomeMethod>

    <label class=fileinput-button ui-button ui-widget ui-state-default ui-corner-all ui-button-text-icon-primary role=button> 

        <span class=ui-button-text>

            <span>Add Documents...</span> 

        </span>

        <input id=upload_button type=file name=postedFiles multiple= />

    </label>

</div>

<div id=UploadMessage data-bind=visible: showMessage> 

    <span>Documents</span>



    <ul data-bind=foreach: upload()>

        <li> 

            <a href=# data-bind=click: $parent.openFile>

                <span data-bind=text: $data.fileName>  </span>

            </a>

        </li>

    </ul>

</div>

Here is the javascript

function Upload(div, additionalParams, successFunc, failureFunc) {

    $('#' + div).fileupload({

        dataType: 'json',

        url: rootPath + 'Upload/SomeMethod',

        formData: additionalParams,

        start: function (e, data) {

            showLoading();

        },

        stop: function (e, data) {

            hideLoading();

        },

        add: function (e, data) {

            data.submit();

        },

        always: function (e, data) {

            var result = data.result;

            if (result.HasError) {

                failureFunc(result.Error);

            } else {

                successFunc(result);

            }

        }

    });

};

The controller method is

public virtual JsonResult SomeMethod(IEnumerable<HttpPostedFileBase> postedFiles, int id)