Thanks.
Yes , I do it as you say.
I HOLD shift, then left click and hold/drag to move a child bone.
And it till doesn't work.
And I found another bug : right click and HOLD a bone/image, the quick-bar will be displayed, but when I release the right mouse key, it will be hidden immediately.
the 3rd : when I zoom in/out the edit-area by mouse-scrolling , it's too fast . scroll little, zoom much .
I use Mac OS X 10.9.
=======================
Update: About IK .
I found why :
When there is the icon (in red circle) , it works well. If no it , doesn't work.