When I group a few objects together, and apply drop shadow to the group, I cannot edit the individual object in the group (cannot pick it to move it or resize it etc) without removing the drop shadow.
There is a workaround that I use in such case:
Select "Shape Tool" (F10) and with Ctrl key select objects that are in the group with drop shadow.
The Shape Tool + Ctrl key can also be used to select objects under many subgroups with just one click (instead of Ctrl + click for each sub group).