I was using the .contents() function to return the DispHTMLDocument, however in IE8 the elem.contentWindow.document did not exist in the DispHTMLWindow2 object.

The problem lies on line 1186:

contents: function(elem){
return jQuery.nodeName(elem,"iframe")?
  elem.contentDocument ||  elem.contentWindow.document:
  jQuery.makeArray(elem.childNodes);
}

Perhaps it should be like this:

contents: function(elem){
  return jQuery.nodeName(elem,"iframe")?
  elem.contentDocument || elem.contentWindow.document || elem.document :
  jQuery.makeArray(elem.childNodes);
}