ASP Button requires two clicks to post back?
<input id="fileUpload" runat="server" type="file"   style="visibility:hidden;" />

<img id="btnBrowse" alt="Choose an photo to upload..." src="images/browse.gif" />

$("#btnBrowse").click(function () {

 $('input[type=file]').click();

});

function addLoadEvent(func) {
    var oldonload = window.onload;
    if (typeof window.onload != 'function') {
         window.onload = func;
    }
    else {
        window.onload = function () {
            if (oldonload) {
                oldonload();
            }
            func();
        }
    }
}
addLoadEvent(whatYouWantToInit);

var whatYouWantToInit_count = 0;
function whatYouWantToInit() {
    if (whatYouWantToInit_count) { return; } // Won't let this function execute twice.
        whatYouWantToInit_count++;
        if ($('yourButton') != null) {
            $('yourButton').onclick = yourButton_click; //the function you want your onclick event to fire.
        }
}