devel-su problems message (su: can't set groups: Operation not permitted)
 

Hi people I have a N9 but when I´m try to change the user to devel-su, I'm recieve the message (su: can't set groups: Operation not permitted), please anybody to help my.

Why, I recieve this message? I need to flash my N9?:confused::confused::confused::confused::confus ed::(:(:(:(:(:(:(