GreaseMonkey & jQueryUI

GreaseMonkey & jQueryUI

I'm trying to inject through GreaseMonkey a script supposed to show a
slider component.
The code is (after including the right css and the @require lines for
jQuery and jQueryUI) :
$("<div id='container'><div class='slider'></div></
div>").appendTo("body");
$(".slider").slider();
But this throws an error:
"Component is not available" ns_result:0x80040111
(NS_ERROR_NOT_AVAILABLE)
Any idea??
--