window.debug.isDebug is null or not an object

I have user control which contains UpdatePanel. For UpdatePanel I have tried to put UpdatePanelAnimationExtender, but there's coming javascipt error which says "window.debug.isDebug is null or not an object". Without UpdatePanelAnimationExtender UpdatePanel is working great. I'm using ASP.NET 2.0 and latest AJAX Framework and ControlToolkit. What could be wrong?

Thanks
juster

You likely have old scripts from an AJAX CTP or Beta cached on your web server or on your browser. Reset IIS and make sure you do a CTRL-F5 on your browser.