AnimationExtender Error Could not be set on property Animations

I am trying to use AnimationExtender.

When I put the AnimationExtender on the page, I get no Error. When I add <Animations> I get no errors. But as soon as I put something in between the opening and closing of the <Animations> the design page show an error saying AnimationExtender could not be set on property Animations.

I refreshed the AjaxToolkit but that did not help.

Please help.

Thanks