IE中的Ajax问题

This chunk of code works fine on FireFox but in IE it gives runtime error when I try to dump the contents from response returned from AJAX response.I am using mootools to make Ajax call.

//on dom ready...  
window.addEvent('domready', function() {  

    /* ajax alert */  <br/>
    $('ajax-alert').addEvent('click', function(event) {
        //prevent the page from changing
        event.stop();
        //make the ajax call
        var req = new Request({
        method: 'get',
        url: $('ajax-alert').get('href'),
        data: { 'do' : '1' },
        onRequest: function() { alert('Request made. Please wait...'); },
        onComplete: function(response) {
            alert(response);// Getting response and able to see that in alert 
            /*line underneath fives runtime error in IE , works fine in FireFox */
            document.getElementById('myDiv').innerHTML  = response;
            //this line gives run time error on IE
        }
    }).send();
}); 

This is likely to happen when the returned response is not a valid X/HTML. I suggest you validate the page with the response returned in it. As Dimitar Christoff has mentioned, watch out for inline elements containing block elements.