[jQuery] $.ajax({..}) throws syntax error in IE7

[Gaz]

Hi all,

This is my first post to the group, so please be gentle :)

For some unknown (to me at least) reason I'm getting a syntax error in  
IE from the following code

     $.ajax({
         type: "POST",
         url: app_config.base_url + "/client/ajax/ 
get_book_details_html/" + btoa(title),
         processData: false,
         data: order,
         async: false,
         success: function(html) {
             $('#related_books').append(html);
             $('#add_book_title').val('');
             hide_loader();
         }
     });

The error is on the first line $.ajax({

This code works perfectly well in all the other browsers I've tested  
it on (FF Mac, FF Windows, Safari Mac).

Anybody got any ideas as to what the problem is?

Cheers,
Gaz.