"Member not found" error in IE8

Why I’m getting this error?
I’ve some init:

	function init() {
		scheduler.config.multi_day = true;
		scheduler.config.first_hour =6;

		scheduler.attachEvent("onContextMenu", function (id, ev){
//			alert("id=" + id);
			if(id == null) return false;
       		return false;

And the error occures when I try to execute this handler under IE:

	function rmenu(id) {
		event = scheduler.getEvent(id);

If you are using recurring events - incoming ID may be a fake one, which consists from

you need only first part for getEvent call

It must be something else.
I’m not using recurring events, the Id is just a number of existing event.
Firefox works ok with the same code and the same events.

Do you have any kind of sample, or demo page where issue can be reconstructed?