Problem with corners in Combination with SlideUp/SlideDown/SlideToggle Function

[Sorcy]

When using corner() in FF3.5.2 the usage of Sliding animations leaves a "barbed" look, as apparently FF rendering engine can not cope. Even uncornering and then recornering does not make the visual error go away, however - changing the opacity via FadeTo of the object sometimes resets the visual. Not sure if this is even an issue with corner.js or a FF bug?!