When I dropped in the test case provided by burnnat, it worked fine. But my grid was still not working. My grid uses the buffered renderer, grouping feature, and filters feature. I commented them out and my grid starting updating correctly. It quit working when I added the grouping feature back in.
If you add the grouping feature to burnnat's code, but don't group by any column, the age won't update in the grid when you click either the Single Param or Double Param button. When you group by a column, the correct value shows up in the grid with the cell dirty marker in the corner and it will update when you click the buttons. Uncheck "Show in groups" and the grid quits updating when clicking the buttons.