Following up from my last post, this is the part of the NetworkManager logs where it seems to fail for me. Unsure if this is the same sort of issue as OP, but it would seem to me that pppd isn't being given enough time to bring up the connection.
NetworkManager[1396]: <info> Activation (ttyO4) Stage 3 of 5 (IP Configure Start) sta rted... NetworkManager[1396]: <info> (ttyO4): device state change: config -> ip-config (reaso n 'none') [50 70 0] NetworkManager[1396]: <warn> (ttyO4): interface ttyO4 not up for IP configuration NetworkManager[1396]: <info> using modem-specified IP timeout: 20 seconds NetworkManager[1396]: <info> starting PPP connection NetworkManager[1396]: <info> pppd started with pid 1596 NetworkManager[1396]: <info> Activation (ttyO4) Stage 4 of 5 (IPv6 Configure Timeout) scheduled... NetworkManager[1396]: <info> Activation (ttyO4) Stage 3 of 5 (IP Configure Start) com plete. NetworkManager[1396]: <info> Activation (ttyO4) Stage 4 of 5 (IPv6 Configure Timeout) started... NetworkManager[1396]: <info> Activation (ttyO4) Stage 4 of 5 (IPv6 Configure Timeout) complete. Plugin /usr/lib/pppd/2.4.6/nm-pppd-plugin.so loaded. nm-pppd-plugin-Message: nm-ppp-plugin: (plugin_init): initializing nm-pppd-plugin-Message: nm-ppp-plugin: (nm_phasechange): status 3 / phase 'serial connection' NetworkManager[1396]: <warn> pppd timed out or didn't initialize our dbus module NetworkManager[1396]: <info> Activation (ttyO4) Stage 4 of 5 (IPv4 Configure Timeout) scheduled... NetworkManager[1396]: <info> Activation (ttyO4) Stage 4 of 5 (IPv4 Configure Timeout) started... NetworkManager[1396]: <info> (ttyO4): device state change: ip-config -> failed (reason 'ip-config-unavailable') [70 120 5] nm-pppd-plugin-Message: nm-ppp-plugin: (nm_phasechange): status 1 / phase 'dead' NetworkManager[1396]: <info> Disabling autoconnect for connection 'GPRS'. NetworkManager[1396]: <warn> Activation (ttyO4) failed for connection 'GPRS' NetworkManager[1396]: <info> Activation (ttyO4) Stage 4 of 5 (IPv4 Configure Timeout) complete. NetworkManager[1396]: <info> (ttyO4): device state change: failed -> disconnected (reason 'none') [120 30 0] NetworkManager[1396]: <info> (ttyO4): deactivating device (reason 'none') [0] NetworkManager[1396]: <info> (ttyO4): modem state changed, 'connected' --> 'disconnecting' (reason: user-requested) nm-pppd-plugin-Message: nm-ppp-plugin: (nm_exit_notify): cleaning up NetworkManager[1396]: <info> (ttyO4): modem state changed, 'disconnecting' --> 'registered' (reason: user-requested)
