After I upgraded to Unity 5.5.0f3.
I can’t select and edit values from Dopesheet from Animation window.
Whenever I click a event of the timeline, then blue line is moved, but values are not changed at all.
Curves works as well. Only Dopesheet is problem. I never experience this before.
Or usage of editing is changed after upgrading?
I’m using Windows version of Unity editor.
Thank you for reading.
Still it bothers me… Whenever I edit a frame, I have to input the exactly frame number to frame shown box. Why did Unity remove selecting a frame by mouse cursor? I don’t understand it. 
Did you file a bug?
It doesn’t seem to be the normal behaviour
Ok, now I get it. Maybe it was me. I upgraded my OS to Windows 10 from 8.1, and it works perfectly. I also found that I have to click the top part of timeline. I’m pretty sure that it was little bit different in the past. (Or, Windows 8.1 problem) Anyway, now I can edit my animation data. Thanks for reply. It’s solved. 
(FYI, still I’m using 5.5.0f3)