'guid' is null or not an object error in IE

'guid' is null or not an object error in IE

I'm new to JQuery (and this forum!) and was really hoping someone can hlep me out with what I think is a simple problem to fix.

I am using the following javascript on a page to play around with some navigation and a div:

$(document).ready(function(){
$(".focusmenu > li").hover(function(e){
switch(e.target.id){
case "tfocuslinkone":
$("#tfocuslinkone").addClass("active");
$("#tfocuslinktwo").removeClass("active");
$("div.tfocuslinkone").fadeIn();
$("div.tfocuslinktwo").css("display", "none");
break;
case "tfocuslinktwo":
$("#tfocuslinkone").removeClass("active");
$("#tfocuslinktwo").addClass("active");
$("div.tfocuslinkone").css("display", "none");
$("div.tfocuslinktwo").fadeIn();
break;
}
},
function () {
// hover requires 2 functions - only need one today
}
);
});

I get an error come up in some versions of IE stating:

'guid' is null or not an object

Can someone help me out please with some example code on how to fix this?