When you put a ComboBoxEx in a grid layout in 0.7 (and possibly later), the drop-down button is normally laid out to the right of the combo itself. This means it can overlap the next column of the grid, or be outside the grid (possibly causing scroll bars to be shown in a dialog). There was a thread about this here.

The cure for this is to set the size of the combo to 100%, and the edit field in the combo to ‘1*.

For example:

   combo.setWidth('100%'); 
   combo.getField().setWidth('1*');

This also has the effect of putting the drop-down button at the right of the edit field.