Hi,

as requested the log files below. I cut out some wlan connection stuff from nm.log.txt.

modem.log.txt:
** Message: Loaded plugin Generic
** Message: Loaded plugin MotoC
** Message: Loaded plugin Gobi
** Message: Loaded plugin Huawei
** Message: Loaded plugin Option High-Speed
** Message: Loaded plugin Option
** Message: Loaded plugin Sierra
** Message: Loaded plugin Novatel
** Message: Loaded plugin Nokia
** Message: Loaded plugin ZTE
** Message: Loaded plugin Ericsson MBM
** Message: (ttyACM0) opening serial device...
** (modem-manager:2350): DEBUG: (ttyACM0): probe requested by plugin 'Generic'
** (modem-manager:2350): DEBUG: (ttyACM0): --> 'AT+GCAP<CR>'
** (modem-manager:2350): DEBUG: (ttyACM0): <-- 'AT+GCAP<CR><CR><LF>ERROR<CR><LF>'
** (modem-manager:2350): DEBUG: Got failure code 100: Unknown error
** (modem-manager:2350): DEBUG: (ttyACM0): --> 'AT+GCAP<CR>'
** (modem-manager:2350): DEBUG: (ttyACM0): <-- 'AT+GCAP<CR><CR><LF>ERROR<CR><LF>'
** (modem-manager:2350): DEBUG: Got failure code 100: Unknown error
** (modem-manager:2350): DEBUG: (ttyACM0): --> 'AT+GCAP<CR>'
** (modem-manager:2350): DEBUG: (ttyACM0): <-- 'AT+GCAP<CR><CR><LF>ERROR<CR><LF>'
** (modem-manager:2350): DEBUG: Got failure code 100: Unknown error
** (modem-manager:2350): DEBUG: (ttyACM0): --> 'ATI<CR>'
** (modem-manager:2350): DEBUG: (ttyACM0): <-- 'ATI<CR><CR><LF>Manufacturer: SAMSUNG ELECTRONICS CORPORATION<CR><LF>Model: GT-Y3100<CR><LF>Revision: Y3100XXHL1 <CR><LF>FTA SW VERSION: Y3100.006<CR><LF>FTA HW VERSION: REV0.1<CR><LF>IMEI: 357580021820329<CR><LF>+GCAP: +CGSM,+DS,+ES<CR><LF><CR><LF>OK<CR><LF>'
** Message: (ttyACM0) closing serial device...
** Message: (Generic): GSM modem /sys/devices/pci0000:00/0000:00:1d.7/usb1/1-7 claimed port ttyACM0
** (modem-manager:2350): DEBUG: Added modem /sys/devices/pci0000:00/0000:00:1d.7/usb1/1-7
** (modem-manager:2350): DEBUG: Exported modem /sys/devices/pci0000:00/0000:00:1d.7/usb1/1-7 as /org/freedesktop/ModemManager/Modems/0
** Message: (ttyACM0) opening serial device...
** (modem-manager:2350): DEBUG: (ttyACM0): --> 'ATZ E0 V1 X4 &C1 +CMEE=1<CR>'
** (modem-manager:2350): DEBUG: (ttyACM0): <-- 'ATZ E0 V1 X4 &C1 +'
** (modem-manager:2350): DEBUG: (ttyACM0): <-- 'CMEE=1<CR><CR><LF>ERROR<CR><LF>'
** (modem-manager:2350): DEBUG: Got failure code 100: Unknown error
** Message: (ttyACM0) closing serial device...

nm.log.txt:
NetworkManager: <info>  starting...
NetworkManager: <info>  modem-manager is now available
NetworkManager:    SCPlugin-Ifupdown: init!
NetworkManager:    SCPlugin-Ifupdown: update_system_hostname
NetworkManager:    SCPluginIfupdown: management mode: unmanaged
NetworkManager:    SCPlugin-Ifupdown: devices added (path: /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/wlan0, iface: wlan0)
NetworkManager:    SCPlugin-Ifupdown: device added (path: /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/wlan0, iface: wlan0): no ifupdown configuration found.
NetworkManager:    SCPlugin-Ifupdown: devices added (path: /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/wmaster0, iface: wmaster0)
NetworkManager:    SCPlugin-Ifupdown: device added (path: /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/net/wmaster0, iface: wmaster0): no ifupdown configuration found.
NetworkManager:    SCPlugin-Ifupdown: devices added (path: /sys/devices/pci0000:00/0000:00:1c.2/0000:03:00.0/net/eth0, iface: eth0)
NetworkManager:    SCPlugin-Ifupdown: device added (path: /sys/devices/pci0000:00/0000:00:1c.2/0000:03:00.0/net/eth0, iface: eth0): no ifupdown configuration found.
NetworkManager:    SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/lo, iface: lo)
NetworkManager:    SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/lo, iface: lo): no ifupdown configuration found.
NetworkManager:    SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/vboxnet0, iface: vboxnet0)
NetworkManager:    SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/vboxnet0, iface: vboxnet0): no ifupdown configuration found.
NetworkManager:    SCPlugin-Ifupdown: end _init.
NetworkManager: Loaded plugin ifupdown: (C) 2008 Canonical Ltd.  To report bugs please use the NetworkManager mailing list.
NetworkManager: Loaded plugin keyfile: (c) 2007 - 2008 Red Hat, Inc.  To report bugs please use the NetworkManager mailing list.
NetworkManager: <info>  Found radio killswitch rfkill0 (at /sys/devices/pci0000:00/0000:00:1c.0/0000:02:00.0/ieee80211/phy0/rfkill0) (driver <unknown>)
NetworkManager: <info>  Wireless now enabled by radio killswitch
NetworkManager:    SCPlugin-Ifupdown: (142101792) ... get_connections.
NetworkManager:    SCPlugin-Ifupdown: (142101792) ... get_connections (managed=false): return empty list.
NetworkManager:    Ifupdown: get unmanaged devices count: 0
NetworkManager: <info>  (wlan0): driver supports SSID scans (scan_capa 0x01).
NetworkManager: <info>  (wlan0): new 802.11 WiFi device (driver: 'ath5k')
NetworkManager: <info>  (wlan0): exported as /org/freedesktop/NetworkManager/Devices/0
NetworkManager: <info>  (wlan0): now managed
NetworkManager: <info>  (wlan0): device state change: 1 -> 2 (reason 2)
NetworkManager: <info>  (wlan0): bringing up device.
NetworkManager: <info>  (wlan0): preparing device.
NetworkManager: <info>  (wlan0): deactivating device (reason: 2).
NetworkManager: <info>  (eth0): carrier is OFF
NetworkManager: <info>  (eth0): new Ethernet device (driver: 'sky2')
NetworkManager: <info>  (eth0): exported as /org/freedesktop/NetworkManager/Devices/1
NetworkManager: <info>  (eth0): now managed
NetworkManager: <info>  (eth0): device state change: 1 -> 2 (reason 2)
NetworkManager: <info>  (eth0): bringing up device.
NetworkManager: <info>  (eth0): preparing device.
NetworkManager: <info>  (eth0): deactivating device (reason: 2).
NetworkManager: <WARN>  device_creator(): /sys/devices/virtual/net/vboxnet0: couldn't determine device driver; ignoring...
NetworkManager: <info>  (ttyACM0): new GSM device (driver: 'cdc_acm')
NetworkManager: <info>  (ttyACM0): exported as /org/freedesktop/NetworkManager/Devices/2
NetworkManager: <info>  (ttyACM0): now managed
NetworkManager: <info>  (ttyACM0): device state change: 1 -> 2 (reason 2)
NetworkManager: <info>  (ttyACM0): deactivating device (reason: 2).
NetworkManager: flush_routes: assertion `iface_idx >= 0' failed
NetworkManager: flush_addresses: assertion `iface_idx >= 0' failed
NetworkManager: <WARN>  default_adapter_cb(): bluez error getting default adapter: The name org.bluez was not provided by any .service files
NetworkManager: <info>  (ttyACM0): device state change: 2 -> 3 (reason 0)

NetworkManager: <info>  Activation (ttyACM0) starting connection 'T-mobile (D1)'
NetworkManager: <info>  (ttyACM0): device state change: 3 -> 4 (reason 0)
NetworkManager: <info>  Activation (ttyACM0) Stage 1 of 5 (Device Prepare) scheduled...
NetworkManager: <info>  Activation (ttyACM0) Stage 1 of 5 (Device Prepare) started...
NetworkManager: <info>  Activation (ttyACM0) Stage 1 of 5 (Device Prepare) complete.
NetworkManager: <WARN>  stage1_prepare_done(): GSM modem connection failed: Unknown error
NetworkManager: <info>  (ttyACM0): device state change: 4 -> 9 (reason 1)
NetworkManager: <info>  Marking connection 'T-mobile (D1)' invalid.
NetworkManager: <info>  Activation (ttyACM0) failed.
NetworkManager: <info>  (ttyACM0): device state change: 9 -> 3 (reason 0)
NetworkManager: <info>  (ttyACM0): deactivating device (reason: 0).
NetworkManager: flush_routes: assertion `iface_idx >= 0' failed
NetworkManager: flush_addresses: assertion `iface_idx >= 0' failed