ANSWER:

I had the same problem, I installed nemo file manager which has admin privileges and dont have a problem although you have to open nemo in a terminal “sudo nemo” enter your password, you now have elevated admin privileges. By the way if I have nemo file manager open without admin privileges and right click open with admin privileges it doesnt work. I have to open nemo in the terminal.

Mik from http://askubuntu.com/questions/298572