Adobe Flex控件缺少垂直滚动条

I have a canvas containing a datagrid. I set horizontal and vertical scroll to 'off' for the canvas, and set both to 'auto' for the DG. This works until I have a larger number of columns in the DG (>=16), then the vertical scroll bar doesn't appear. Anyone seen this and, better yet, have an answer?I have a canvas containing a datagrid. I set ho