field not visible in grid columns

Hi All ,

I have a very strange issue . I edited one form and added one table field to that form
I have checked the option allowed in grid and also initially hidden (overview) session,but
when I am starting the session the field is not shown in grid's hidden column . I have never faced
such an issue and found it to be a bit strange .

I will be very much grateful if any one can help me on this