Column headers alignment with X scrolling

See http://fleming-group.com/Hidden/New/Test.htm and debug code ehetuv. I'm trying to get the headers lined up with the columns; the misalignment is small but not acceptable in Firefox and Opera, and more than a column width and definitely not acceptable in IE9. I've messed with various values of sScrollXInner, including leaving it out, but it seems that nothing helps. ???