Extra column appear in the ActiveWidget grid

I am using ActiveWidget grid in my current project.
Assume that I have 4 columns in my grisd and each has got the width 0f 100 px and the total width is 400px.

When I do this there is an extra column appears at the end of the 4th column. ie 5th column is appearing. If I reduce the width of the grid then Horizontal scroll bar is coming. If I increase the width then the 5th column looks visible.

Do you guys have any solution for that.......

Screenshot?

Take into account vertical scrollbar. By my calculation 24px (i.e. make width of grid 424px). You will still get a small gap between last column and scrollbar but you will have to dive into AW stylesheets to get rid of that.