Serial port selection unaviable since 1.6.11 version

Hello,
I am using arduino IDE on xubuntu 64bits.
For versions after 1.6.11 the serial port selection is grayed. I can not select the serial port and I am stucked with /dev/ttyUSB0. If the port change or if I have more than one board connected, I can not download a sketch any more.
I have tried every release after 1.6.11 on several machines and I have the same problem.
I works perfectly with 1.6.11.
Has anyone have the same problem ?
Thank you,
Philippe