Comment 9 for bug 949597

It is not enough to add the user to dialout. You also have to sudo apt-get remove modemmanager
Check this: http://askubuntu.com/questions/133235/how-do-i-allow-non-root-access-to-ttyusb0-on-12-04
and this: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/662881

I'm using ubuntu 13.04 by the way.