Odd javascript error from IE

[Ryland]

The page I am working on has a tabbed interface which works fine using FF but when viewed from IE I receive an "object required" error message at the SetCurrent("Users Table") call.

My page has FindCurrent() being called at page load which, if it can match the page title up with a specific list it calls a 2nd function which changes the id on a specific list item so that it shows up as "Selected".

Does anybody have an idea as to what I am doing wrong?

       function SetCurrent(title) 
       {
       // Find all list items on the page
       	var oSubjects = document.getElementsByTagName("li");
       	
       	// Cycle through the list items
 		for (var i = 0; i < oSubjects.length; i++)
         {
            var oSubject = oSubjects.item(i);
            var sID = oSubject.getElementsByTagName("span");
            
            // Check the text displayed on them to see if it matches the title passed in
            if ( sID.item(0).innerHTML == title )  {      
       			oSubject.id="current"; // Sets the list item as the "Current" one.
       		}
         }
       }       
       
       function FindCurrent()
       {
       var titleElement = document.getElementsByTagName("title")[0];
       
       // Matching the TITLE of the page up.  If it is found then send in the text displayed on the Tab which is "current"
       if ( titleElement.firstChild.data == "User Table" ) {
       	SetCurrent("Users Table");
       	} else if ( titleElement.firstChild.data == "Table List" ) {
       	SetCurrent("View Tables");
       	} else if ( titleElement.firstChild.data == "Event Table" ) {
       	SetCurrent("Event Table");
       	} else if ( titleElement.firstChild.data == "Inventory Table" ) {
       	SetCurrent("Inventory Table");
       	}
       }