Drillthough multiple selections

I have a dashboard with several graphs showing various measures from some survery data broken down by gender .  I would like to be able to select multiple chunks from these graphs and drill through but it seems like it only drills through on the part of the graph I right click on even if I have control-clicked several selections.  I swear this was working yesterday and then I added a few new graphs and now it's not.   What am I missing?