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

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


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.