Arrow past last row

I have searched the listings but can't figure out why I am able to down arrow past the last row in the grid. On sample grids, the cursor stops on the last row. But on my grids, I am able to keep going. I loose the highlite, but the grid does not scroll any further. In the event code for selectionChanged, I have it update the status with the current selection/index and it shows that the number keeps increasing past the total number of rows in the grid. And when you up arrow, the number decrements until it gets back into the visible row range then I get my highliting back. It doesn't matter if I have more rows then will show on the grid of just a couple, as long as I have more then one row I see this behavior. I know it's some simple thing I am doing (or not doing) that is causing this. I have tried setting the number of rows for the grid with both setRowCount(xx) and setRowProperty("count", xx) and I get the same behavior with both.

So, the question is "What am I missing here?"

Thanks