I could proceed to the next screen by changing advanced settings in user mapping section. My changes are : Posix Mode: No Group Filter : (objectClass=Group)
Surprisingly, once I reached to the Add Administrator screen, after coming back I reset these fields and it was still working fine. I wonder if after restarting the server it will work or not.
Also in the Step 1, make sure in the hostname you provide the ip address of your machine. With localhost it dint work for me.
Thanks, Hope it helps anyways!