[ubuntu] cannot elevate privilege in gui in a xrdp session topic

whenever I click a button that requires elevated privilege, a windows asking for password is supposed to prompt. But it never prompt when I am connected using xrdp.
I can use sudo in terminal without any problem using xrdp.
If i use sudo to call the gui out, for example, sudo mate-control-center, the window will stop responding...

login locally:
click mate-control-center>click users and groups>click change>asked for password

login remotely using xrdp:
click mate-control-center>click users and groups>click change>nothing happen

login remotely using xrdp:
sudo mate-control-center>click users and groups>users settings window stop responding


I am using ubuntu14.04
unity cannot work with xrdp, so I installed ubuntu-mate