Bug on footer labels applied to a grid

The footer has an overlapping of labels during the scrolling. To reproduce the problem you can try the old demo posted in http://tracker.zkoss.org/browse/ZK-320.
This ptoblem is present in Chrome 13.0.782 and not in IE9, where, on the other hand, is present a strange modification of the heigth of the footer during the same srolling test.