(Copied out of the forums, since this seems like a better place to track bugs.)
Allan, I think I have found a bug related to bScrollCollapse. Basically, when I set sScrollX to 100%, sScrollY to a pixel value greater than necessary to render the table, and bScrollCollapse to true, I can see the space where the vertical scrollbar would be. If I turn off any of those features then the space goes away and the table expands to the width of its container; this is the expected behavior. I'm currently using the latest 1.9 dev, but I'm pretty sure I saw this in 1.8 as well.
This bug appears for me on page load in chromium. When I test with Firefox 10, I can make it happen by forcing the table to redraw itself by sorting, searching, paging.
Example here: http://live.datatables.net/imukev
Yup - this is certainly a bug - been in since infinite scrolling was first introduced actually :-(. Thanks for filing this issue!
Basically the issue is that since no scrolling is needed on the first draw then there are no scrollbars - thus there can be no scroll event to load more data. The workaround for the moment is to increase iDisplayLength to something more suitable for the sScrollY size - but the real fix is for DataTables to compute the number of rows that should be shown not he first draw.
Infinite scrolling ( bScrollInfinite ) has been removed in DataTables 1.10, which I've just merged to master (its almost beta ready, not released yet), due to issues such as this. Infinite scrolling has been replaced with the Scroller extra now, as infinite scrolling was not an acceptable solution and it was holding DataTables back in terms of technical advancement (it was deprecated in 1.9).
As such, I'm afraid this bug isn't going to be addressed as this feature is no longer in DataTables. So closing bug.