Android tethering does not work when network manager is running

After lost many hours trying to discover why the USB Tethering of my LG E615f and my friend's LG E470 android phones, I just realised:

(with cable unplugged)
alex@ubuntu_asus:~$ sudo start network-manager
network-manager start/running, process 3843
(plugging the cable and start tethering)
alex@ubuntu_asus:~$ ip link
(...)
9: usb0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000
    link/ether 02:61:5a:5d:30:2c brd ff:ff:ff:ff:ff:ff

But, when I try without network-manager
(with cable unplugged)
alex@ubuntu_asus:~$ sudo stop network-manager
network-manager stop/waiting
(plugging again and starting tethering)
alex@ubuntu_asus:~$ ip addr
(...)
10: usb0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN qlen 1000
    link/ether 02:61:5a:5d:30:2c brd ff:ff:ff:ff:ff:ff

I tried many times and aways got the same result.
I've found this problem in both raring and Ubuntu 14.04, but only in raring I have tested this soluction.

alex@ubuntu_asus:~$ lsb_release -rd
Description: Ubuntu 12.04.4 LTS
Release: 12.04
alex@ubuntu_asus:~$ apt-cache policy network-manager
network-manager:
  Installed: 0.9.4.0-0ubuntu4.3
  Candidate: 0.9.8.0-0ubuntu6.1
  Version table:
     0.9.8.0-0ubuntu6.1 0
        500 http://old-releases.ubuntu.com/ubuntu/ raring-updates/main amd64 Packages
     0.9.8.0-0ubuntu6 0
        500 http://old-releases.ubuntu.com/ubuntu/ raring/main amd64 Packages
 *** 0.9.4.0-0ubuntu4.3 0
        100 /var/lib/dpkg/status