[jQuery] jQuery validation error: 'settings' is null or not an object

[NovoGeek]

Hi all,
I'm using jQuery validation plugin and everything works fine in
Firefox. But in IE (7&8), when I try to validate my form, I get the
error - ['settings' is null or not an object].

I'm using simple rules like this:

$("#FormID").validate({
                rules: {
                    FirstNameText:"required"
                },
                messages:{
                    FirstNameText: "Please enter first name"
                }
            });

I searched for similar posts and found this:
http://groups.google.com/group/jquery-en/browse_thread/thread/831feb27923dc32c
. However, a convincing answer is not given.

Can some one tell me why this error is coming?