I 'm not sure if it is a bug, but I do feel there was somewhere went wrong in my upgrading.
I also tried to have a new installed 2.1, it works fine, here is the screen shot for the new installed 2.1 add block page. Which is normal.
Here is my live store upgraded from 2.0.15
The group cannot be selected. This may cause the add block failed.
Is there any one who can help?