I have a very similar problem. Since upgrading to 9.04 when trying to connect using Mobile in NetworkManger. Sometimes it will work, and other times not. I can plug in the phone and it may connect successfully. Then I disconnect and unplug, then replug and try again and the Mobile connectrion may not even show up in NetworkManager. The following appears in syslog: Successful: Aug 3 09:45:34 mike-laptop kernel: [29596.728079] usb 2-1: new full speed USB device using uhci_hcd and address 8 Aug 3 09:45:35 mike-laptop kernel: [29596.911410] usb 2-1: configuration #1 chosen from 1 choice Aug 3 09:45:35 mike-laptop kernel: [29596.921401] cdc_acm 2-1:1.0: ttyACM0: USB ACM device Aug 3 09:45:36 mike-laptop nm-system-settings: SCPlugin-Ifupdown: device added (udi: /org/freedesktop/Hal/devices/usb_device_22b8_3002_noserial_if0_serial_unknown_0_1, iface: (null)): iface not found Aug 3 09:45:36 mike-laptop NetworkManager: (ttyACM0): found serial port (udev:GSM hal:GSM) Aug 3 09:45:36 mike-laptop NetworkManager: (ttyACM0): new Modem device (driver: 'cdc_acm') Aug 3 09:45:36 mike-laptop NetworkManager: (ttyACM0): exported as /org/freedesktop/Hal/devices/usb_device_22b8_3002_noserial_if0_serial_unknown_0_1 Aug 3 09:45:39 mike-laptop NetworkManager: (ttyACM0): device state change: 1 -> 2 Aug 3 09:45:40 mike-laptop NetworkManager: (ttyACM0): deactivating device (reason: 2). Aug 3 09:45:40 mike-laptop NetworkManager: nm_system_device_flush_ip4_routes_with_iface: assertion `iface_idx >= 0' failed Aug 3 09:45:40 mike-laptop NetworkManager: nm_system_device_flush_ip4_addresses_with_iface: assertion `iface_idx >= 0' failed Aug 3 09:45:40 mike-laptop NetworkManager: (ttyACM0): device state change: 2 -> 3 Aug 3 09:45:49 mike-laptop NetworkManager: Activation (ttyACM0) starting connection 'Vodafone' Aug 3 09:45:49 mike-laptop NetworkManager: (ttyACM0): device state change: 3 -> 4 Aug 3 09:45:49 mike-laptop NetworkManager: Activation (ttyACM0) Stage 1 of 5 (Device Prepare) scheduled... Aug 3 09:45:49 mike-laptop NetworkManager: Activation (ttyACM0) Stage 1 of 5 (Device Prepare) started... Aug 3 09:45:49 mike-laptop NetworkManager: [1249249549.061475] nm_serial_device_open(): (ttyACM0) opening device... Aug 3 09:45:49 mike-laptop NetworkManager: Activation (ttyACM0) Stage 1 of 5 (Device Prepare) complete. Aug 3 09:45:49 mike-laptop NetworkManager: (ttyACM0): powering up... Aug 3 09:45:49 mike-laptop NetworkManager: Registered on Home network Aug 3 09:45:49 mike-laptop NetworkManager: Associated with network: +COPS: 0,0,"vodafone NZ" Aug 3 09:45:49 mike-laptop NetworkManager: Connected, Woo! Aug 3 09:45:49 mike-laptop NetworkManager: Activation (ttyACM0) Stage 2 of 5 (Device Configure) scheduled... Aug 3 09:45:49 mike-laptop NetworkManager: Activation (ttyACM0) Stage 2 of 5 (Device Configure) starting... Aug 3 09:45:49 mike-laptop NetworkManager: (ttyACM0): device state change: 4 -> 5 Aug 3 09:45:49 mike-laptop NetworkManager: Starting pppd connection Aug 3 09:45:49 mike-laptop NetworkManager: [1249249549.980881] nm_ppp_manager_start(): Command line: /usr/sbin/pppd nodetach lock nodefaultroute user web ttyACM0 noipdefault noauth usepeerdns lcp-echo-failure 0 lcp-echo-interval 0 ipparam /org/freedesktop/NetworkManager/PPP/2 plugin /usr/lib/pppd/2.4.4/nm-pppd-plugin.so Aug 3 09:45:49 mike-laptop NetworkManager: [1249249549.983901] nm_ppp_manager_start(): ppp started with pid 17024 Aug 3 09:45:49 mike-laptop NetworkManager: Activation (ttyACM0) Stage 2 of 5 (Device Configure) complete. Aug 3 09:45:49 mike-laptop pppd[17024]: Plugin /usr/lib/pppd/2.4.4/nm-pppd-plugin.so loaded. Aug 3 09:45:50 mike-laptop pppd[17024]: pppd 2.4.5 started by root, uid 0 Aug 3 09:45:50 mike-laptop pppd[17024]: Using interface ppp0 Aug 3 09:45:50 mike-laptop pppd[17024]: Connect: ppp0 <--> /dev/ttyACM0 Aug 3 09:45:50 mike-laptop NetworkManager: (ttyACM0): device state change: 5 -> 6 Aug 3 09:45:50 mike-laptop pppd[17024]: PAP authentication succeeded Aug 3 09:45:50 mike-laptop NetworkManager: (ttyACM0): device state change: 6 -> 7 Aug 3 09:45:56 mike-laptop pppd[17024]: Cannot determine ethernet address for proxy ARP Aug 3 09:45:56 mike-laptop pppd[17024]: local IP address 124.6.219.235 Aug 3 09:45:56 mike-laptop pppd[17024]: remote IP address 192.168.100.101 Aug 3 09:45:56 mike-laptop pppd[17024]: primary DNS address 202.73.206.16 Aug 3 09:45:56 mike-laptop pppd[17024]: secondary DNS address 202.73.198.16 Aug 3 09:45:56 mike-laptop NetworkManager: PPP manager(IP Config Get) reply received. Aug 3 09:45:56 mike-laptop NetworkManager: Activation (ttyACM0) Stage 4 of 5 (IP Configure Get) scheduled... Aug 3 09:45:56 mike-laptop NetworkManager: Activation (ttyACM0) Stage 4 of 5 (IP Configure Get) started... Aug 3 09:45:56 mike-laptop NetworkManager: Activation (ttyACM0) Stage 5 of 5 (IP Configure Commit) scheduled... Aug 3 09:45:56 mike-laptop NetworkManager: Activation (ttyACM0) Stage 4 of 5 (IP Configure Get) complete. Aug 3 09:45:56 mike-laptop NetworkManager: Activation (ttyACM0) Stage 5 of 5 (IP Configure Commit) started... Aug 3 09:45:57 mike-laptop NetworkManager: (ppp0): writing resolv.conf to /sbin/resolvconf Aug 3 09:45:57 mike-laptop NetworkManager: (ttyACM0): device state change: 7 -> 8 Aug 3 09:45:57 mike-laptop NetworkManager: (ppp0): writing resolv.conf to /sbin/resolvconf Aug 3 09:45:57 mike-laptop NetworkManager: Policy set 'Vodafone' (ppp0) as default for routing and DNS. Aug 3 09:45:57 mike-laptop NetworkManager: Activation (ttyACM0) successful, device activated. Aug 3 09:45:57 mike-laptop NetworkManager: Activation (ttyACM0) Stage 5 of 5 (IP Configure Commit) complete. Unsuccessful: Aug 3 09:50:47 mike-laptop nm-system-settings: SCPlugin-Ifupdown: device added (udi: /org/freedesktop/Hal/devices/usb_device_22b8_3002_noserial_if0_serial_unknown_0_2, iface: (null)): iface not found Aug 3 09:50:47 mike-laptop NetworkManager: (ttyACM0): found serial port (udev: hal:GSM) Aug 3 09:50:47 mike-laptop NetworkManager: (ttyACM0): ignoring due to lack of probed mobile broadband capabilties Very strange. I am using a Motorola Razor V3x. If I use GNOME PPP it works every time.