I found bug if you are using TableTools2 and Datatables 1.9.0 with option "sRowSelect": "single". Then COPY button of the TableTools won't copy those rows in the table.
Good find - thanks for that. I've just committed a fix which is now available in the TableTools nightly build ( http://datatables.net/download ).
Do remember that if you want the copy to only copy selected rows then you need to set bSelectedOnly: true for the button (it is false by default and thus will copy all rows - although not in the case above due to the bug!).