Unwanted data injected into datagrid textbox

I'm happy to announce that we figured out what is happening with the 'unwanted data injected into datagrid textbox' and it is now fixed on our site.

I found the cause purely by accident, when testing on an older server that is significantly slower than our production web server. I found that I could click the Next button multiple times while I waited 5-8 seconds between page loads. Whenever I did, it "jumped" the same number of pages and copied the values from the first page to all the subsequent pages that were "touched" in the transaction. Nothing on the screen would ever suggest to the user that such a thing had occurred.

Mr. Barker from sqlwork.com got me on the right track when he suggested duplicate postback was the likely problem.

At the bottom of the page, just before the closing HTML tag, we added this javascript code, which disables all buttons on the page and displays a "Processing..." message until the next page loads:

<script language="javascript">
    /* Code to fix multi-click issue */
    
    // handle the unload of the form
    window.attachEvent("onbeforeunload", disableWindowControlsOnUnload);
    
    // loop through relevant input controls and make sure the users do attempt a postback
    var elementCollection = document.getElementsByTagName("input");
    if ( elementCollection != null )
    {
        for ( var i = 0; i < elementCollection.length; i++ )
        {
            var element = elementCollection(i);
            if ( element.type == "submit" || element.type == "button" )
            {
                element.attachEvent("onclick", disableWindowControlsOnClick);
                element.attachEvent("ondblclick", handleDoubleClick);
            }
        }
    }

    // this method used to disable any input controls from firing
    function disableWindowControlsOnUnload()
    {
        document.body.style.cursor = "wait";
        for ( var j = 0; j < document.forms.length; j++ )
        {
            var elementCollection = document.forms(j).getElementsByTagName("input");            
            for ( var i = 0; i < elementCollection.length; i++ )
            {
                var element = elementCollection(i);
                if ( thisElement.type == "submit" || thisElement.type == "button" )
                    element.disabled = true;
            }
        }
        
        return true;
    }

    // this will make sure no events create a double post scenario
    var bubbleEvent = true;
    function disableWindowControlsOnClick()
    {
        if ( bubbleEvent == true )
        {
            document.body.style.cursor = "wait";
            showProcessingBanner();
            bubbleEvent = false;
        }
        else
        {
            window.event.cancelBubble = false;
            window.event.returnValue = false;
        }
    }
    
    function handleDoubleClick()
    {
            window.event.cancelBubble = false;
            window.event.returnValue = false;
    }
    
    
    function showProcessingBanner()
    {
        var bannerElement = "<div style='position:absolute; z-index:99; border-style:solid; background-color:white; width:400px; height:200px;'></div>";
        var banner = document.createElement(bannerElement);
        
        banner.innerHTML = "<span style='color:black; font-size:large; vertical-align:middle;'><center><br><br><br>Processing...</center></span>";
        banner.style.left = ( window.screen.availWidth / 2 ) - 200;
        banner.style.top  = ( window.screen.availHeight / 2 ) - 100;
        document.body.insertBefore(banner);
    }
    
    </script>