Shape key and Center Cursor

I am having problem with trying to move object center once I get into Shape key mode. That is, after I add new shape key, I try to move the object center so that there is a new center point for rotation. The center must be moved for controlled rotation of sets of vertices. You know, bending a simple tab.

I can “Center Cursor” fine if I don’t get into Shape Key. And, the tab can be rotated to any given angle. What’s the problem here?