Comment 7 for bug 884829

It's not a kernel bug or something. Must be something about NetworkManager.

Kernel: 3.5.1
DE: Cinnamon 1.4UP3

network-manager 0.9.4.0-0ubuntu4.1
network-manager-gnome 0.9.4.1-0ubuntu2
network-manager-pptp 0.9.4.0-0ubuntu1

Bus 002 Device 005: ID 12d1:1404 Huawei Technologies Co., Ltd.
Couldn't open device, some information will be missing
Device Descriptor:
  bLength 18
  bDescriptorType 1
  bcdUSB 2.00
  bDeviceClass 0 (Defined at Interface level)
  bDeviceSubClass 0
  bDeviceProtocol 0
  bMaxPacketSize0 64
  idVendor 0x12d1 Huawei Technologies Co., Ltd.
  idProduct 0x1404
  bcdDevice 0.00
  iManufacturer 3
  iProduct 2
  iSerial 0
  bNumConfigurations 1

Syslog:

Aug 15 11:39:59 black NetworkManager[911]: <info> Activation (ttyUSB0) starting connection 'T-Mobile(Telekom) Vorgabe'
Aug 15 11:39:59 black NetworkManager[911]: <info> (ttyUSB0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
Aug 15 11:39:59 black NetworkManager[911]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) scheduled...
Aug 15 11:39:59 black NetworkManager[911]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) started...
Aug 15 11:39:59 black NetworkManager[911]: <info> (ttyUSB0): device state change: prepare -> need-auth (reason 'none') [40 60 0]
Aug 15 11:39:59 black NetworkManager[911]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) complete.
Aug 15 11:39:59 black NetworkManager[911]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) scheduled...
Aug 15 11:39:59 black NetworkManager[911]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) started...
Aug 15 11:39:59 black NetworkManager[911]: <info> (ttyUSB0): device state change: need-auth -> prepare (reason 'none') [60 40 0]
Aug 15 11:39:59 black NetworkManager[911]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) complete.
Aug 15 11:39:59 black modem-manager[837]: <info> (ttyUSB0) opening serial port...
Aug 15 11:39:59 black modem-manager[837]: <info> Modem /org/freedesktop/ModemManager/Modems/0: state changed (disabled -> enabling)
Aug 15 11:40:00 black modem-manager[837]: <warn> (ttyUSB0): failed to query SMS mode, assuming text mode
Aug 15 11:40:00 black modem-manager[837]: <warn> (ttyUSB0): failed to enable USSD notifications.
Aug 15 11:40:00 black modem-manager[837]: <info> Modem /org/freedesktop/ModemManager/Modems/0: state changed (enabling -> disabled)
Aug 15 11:40:00 black modem-manager[837]: <info> (ttyUSB0) closing serial port...
Aug 15 11:40:00 black modem-manager[837]: <info> (ttyUSB0) serial port closed
Aug 15 11:40:00 black NetworkManager[911]: <warn> GSM modem enable failed: (32) Failed to find a usable modem character set
Aug 15 11:40:00 black NetworkManager[911]: <info> (ttyUSB0): device state change: prepare -> failed (reason 'modem-init-failed') [40 120 28]
Aug 15 11:40:00 black NetworkManager[911]: <info> Marking connection 'T-Mobile(Telekom) Vorgabe' invalid.
Aug 15 11:40:00 black NetworkManager[911]: <warn> Activation (ttyUSB0) failed.
Aug 15 11:40:00 black NetworkManager[911]: <info> (ttyUSB0): device state change: failed -> disconnected (reason 'none') [120 30 0]
Aug 15 11:40:00 black NetworkManager[911]: <info> (ttyUSB0): deactivating device (reason 'none') [0]
Aug 15 11:40:00 black NetworkManager[911]: nm_system_iface_flush_routes: assertion `ifindex > 0' failed
Aug 15 11:40:00 black NetworkManager[911]: nm_system_iface_flush_addresses: assertion `ifindex > 0' failed