As for the last issue, related to IE10, it seems to be a specific behaviour/feature of the browser: when the container width is too small to display the entire width of a scrollable table (or any scrollable container), then the (vertical) scrollbar is placed inside the inner width of the table to save some space, but this messes with our alignment calculations. If the outer container is wide enough, then the scrollbar is displayed outside the inner width of the table, as all other browsers do. It's not possible to determine if the scrollbar is inside or outside of the container, and the threshold to display the scrollbar inside is not very precise. There's not much we can do about this particular browser behaviour but to simply increase the width of the outer container, in this case the ace:dialog. Committed this modification to the ace:dataTable Scrolling demo in the showcase to the 4.0 trunk at revision 41275, to the 3.3 EE maintenance branch at revision 41276 and to the P02 tag at revision 41277.
For this particular demo, if we simply removed the 'rows' attribute (and the 'paginator' attribute too, since it wouldn't be needed) from the table in the dialog, there wouldn't be misalignments. What happens is that when scrollable=true and a specified height is significantly larger than the height required to display the number of specified rows, the headers tend to expand to cover the area above of the scrollbar, rendering the header and the body columns misaligned.