Arduino run under Xubuntu, but with 2 problems.

I have a little Laptop with 1 Go RAM, Windows 7 as OS. It is slow. In order to use it more efficiently with IDE Arduino, I have installed Xubuntu 14.04 on it, dual boot with Grub. Then Arduino software by the sudo apt-get [...] arduino-core; this work well.
Starting arduino by the menu, or double click on a .ino file ask for the su password, but because added/needed software are not properly loaded, the serial port is not seen after all. The menu "serial port" is grayed.

Starting arduino software with terminal cmd line: sudo arduino
gives "Error parsing gtk-icon-sizes string: ' ' "
Then the program starts with the serial port seen as a \dev\ttyUSB0 one. And it works.

My question #1: what config or setup can correct this?

Then, the version loaded by the apt-get is + dfsg2-2
Question #2: how can I have the latest version for Yun?

You need to check which groups your user needs to belong to so that it can see the serial ports.