Desde hace un par de semanas he tenido problemas para conectarma a internet usando mi bam de iusacell atravez del networkmanager, conecto la bam le doy conectar y empieza conectar 2 seg despues se detiene, sin mandar ningun error ni nada, pero si me conecto atravez de la consola usando wvdial conecta bien, alguien sabe como resolver este problema.

¿Qué versión de NetworkManager? ¿Que distribución de GNU/Linux? ¿está actualizado al día tu sistema?

Fedora 12 X86_64 actualizado hasta este momento, NetworkManager-0.7.998-2.git20100106, Bam atravez del celular K1m es de iusacell

Publica la salida de /var/log/messages al momento de intentar conectarte.

La salida que me muestra es esto:

Mar 10 16:05:28 timelap modem-manager: (ttyACM0) opening serial device...
Mar 10 16:05:29 timelap modem-manager: (ttyACM0) closing serial device...
Mar 10 16:05:29 timelap modem-manager: (Generic): CDMA modem /sys/devices/pci0000:00/0000:00:1a.0/usb3/3-1 claimed port ttyACM0
Mar 10 16:05:29 timelap NetworkManager: <info> (ttyACM0): new CDMA device (driver: 'cdc_acm'
Mar 10 16:05:29 timelap NetworkManager: <info> (ttyACM0): exported as /org/freedesktop/NetworkManager/Devices/2
Mar 10 16:05:29 timelap NetworkManager: <info> (ttyACM0): now managed
Mar 10 16:05:29 timelap NetworkManager: <info> (ttyACM0): device state change: 1 -> 2 (reason 2)
Mar 10 16:05:29 timelap NetworkManager: <info> (ttyACM0): deactivating device (reason: 2).
Mar 10 16:05:29 timelap NetworkManager: <info> (ttyACM0): device state change: 2 -> 3 (reason 0)
Mar 10 16:05:32 timelap NetworkManager: <info> Activation (ttyACM0) starting connection 'Iusacell connection'
Mar 10 16:05:32 timelap NetworkManager: <info> (ttyACM0): device state change: 3 -> 4 (reason 0)
Mar 10 16:05:32 timelap NetworkManager: <info> Activation (ttyACM0) Stage 1 of 5 (Device Prepare) scheduled...
Mar 10 16:05:32 timelap NetworkManager: <info> Activation (ttyACM0) Stage 1 of 5 (Device Prepare) started...
Mar 10 16:05:32 timelap NetworkManager: <info> Activation (ttyACM0) Stage 1 of 5 (Device Prepare) complete.
Mar 10 16:05:32 timelap modem-manager: (ttyACM0) opening serial device...
Mar 10 16:05:32 timelap modem-manager: Modem /org/freedesktop/ModemManager/Modems/0: state changed (disabled -> enabling)
Mar 10 16:05:32 timelap modem-manager: Your CDMA modem does not support +CMEE command
Mar 10 16:05:32 timelap modem-manager: Modem /org/freedesktop/ModemManager/Modems/0: state changed (enabling -> enabled)
Mar 10 16:05:32 timelap modem-manager: Modem /org/freedesktop/ModemManager/Modems/0: state changed (enabled -> registered)
Mar 10 16:05:32 timelap modem-manager: Modem /org/freedesktop/ModemManager/Modems/0: state changed (registered -> connecting)
Mar 10 16:05:33 timelap modem-manager: Modem /org/freedesktop/ModemManager/Modems/0: state changed (connecting -> connected)
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 2 of 5 (Device Configure) scheduled...
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 2 of 5 (Device Configure) starting...
Mar 10 16:05:33 timelap NetworkManager: <info> (ttyACM0): device state change: 4 -> 5 (reason 0)
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 2 of 5 (Device Configure) successful.
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 3 of 5 (IP Configure Start) scheduled.
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 2 of 5 (Device Configure) complete.
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 3 of 5 (IP Configure Start) started...
Mar 10 16:05:33 timelap NetworkManager: <info> (ttyACM0): device state change: 5 -> 7 (reason 0)
Mar 10 16:05:33 timelap NetworkManager: <info> Starting pppd connection
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 4 of 5 (IP6 Configure Get) scheduled...
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 3 of 5 (IP Configure Start) complete.
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 4 of 5 (IP6 Configure Get) started...
Mar 10 16:05:33 timelap NetworkManager: <info> Activation (ttyACM0) Stage 4 of 5 (IP6 Configure Get) complete.
Mar 10 16:05:33 timelap pppd[2158]: Plugin /usr/lib64/pppd/2.4.5/nm-pppd-plugin.so loaded.
Mar 10 16:05:34 timelap kernel: PPP generic driver version 2.4.2
Mar 10 16:05:34 timelap pppd[2158]: pppd 2.4.5 started by root, uid 0
Mar 10 16:05:34 timelap pppd[2158]: Using interface ppp0
Mar 10 16:05:34 timelap pppd[2158]: Connect: ppp0 <--> /dev/ttyACM0
Mar 10 16:05:34 timelap pppd[2158]: MPPE required, but MS-CHAP[v2] auth not performed.
Mar 10 16:05:34 timelap pppd[2158]: Connection terminated.
Mar 10 16:05:34 timelap NetworkManager: <info> (ttyACM0): device state change: 7 -> 9 (reason 13)
Mar 10 16:05:34 timelap NetworkManager: <info> Marking connection 'Iusacell connection' invalid.
Mar 10 16:05:34 timelap NetworkManager: <info> Activation (ttyACM0) failed.
Mar 10 16:05:34 timelap NetworkManager: <info> (ttyACM0): device state change: 9 -> 3 (reason 0)
Mar 10 16:05:34 timelap NetworkManager: <info> (ttyACM0): deactivating device (reason: 0).
Mar 10 16:05:34 timelap modem-manager: Modem /org/freedesktop/ModemManager/Modems/0: state changed (connected -> disconnecting)
Mar 10 16:05:34 timelap NetworkManager: <info> Policy set 'Auto SurtOcciWEJ1' (wlan0) as default for routing and DNS.
Mar 10 16:05:35 timelap modem-manager: Modem /org/freedesktop/ModemManager/Modems/0: state changed (disconnecting -> registered)
Mar 10 16:05:35 timelap pppd[2158]: Exit.

Prove desde otra cuenta en la misma maquina y si conecta.

Tu problema parece estar en:

Mar 10 16:05:34 timelap pppd[2158]: MPPE required, but MS-CHAP[v2] auth not performed.
Mar 10 16:05:34 timelap pppd[2158]: Connection terminated.

Eso indica que se está haciendo una solicitud para autenticar con usuario y clave de acceso al tratar de conectarte, lo cual es un tanto extraño, pues se supone no requieres autenticar. Asigna #777 como número a marcar en la configuración del modem 3G.

Ya tiene configurado ese numero para marcar, el problema se resolvio efectivamente quitando MS-CHAP de la configuracion, solo que se desconectaba cada 5 min, eso se elimino quitando la opcion de envio de paquetes echo.