problem with sScrollY: 100px property

Hi,
I am facing a problem after adding sScrollY: 100px property. I want to display some details as a pop up and there I want to add DATATABLE.
In this, I am adding heading through JQuery . I am getting the popup correctly before adding sScrollY property. But after adding this, I am not getting the heading as propertly. Width of the heading is less that the toltal width of the table. When I checked, the width is 100% for that <tr>

Please help me to get a solution