If you prefer the Edit Group Box pallette buttons rather than the shortcut keys (CG, FG, RG, AG), try this to restore the pallette in Revit 2011:
1. Within the same Revit session that you are having difficulty with your Edit Group box, open a NEW Revit file (.rvt) with an empty blank template file (.rte). You can press CTRL+N as well.
2. Draw a couple of lines and create a simple group ('CG' are the shortcut keys).
3. Select the simple line group and Edit Group.
4. The Edit Group box should hopefully appear somewhere in its free-floating position.
5. Drag and Dock the Edit Group Box pallette up onto the ribbon.
6. Return to your other Revit file (.rvt) that was giving you trouble, and try to Edit Group again.
7. The Edit Group Box pallette should now be docked to your ribbon.