Mobile Broadband auto-connect doesn't

[Rick Jones <rick activeservice co uk>]

I have a MB connection set for "connect automatically", on which basis I think it should
connect automatically when the USB modem is plugged in. But it only does this very
occasionally, less than one time in ten. Usually it just sits there and requires
manual connection.

I suppose this might be a problem outside NM, but according to the log NM gets all
the right notifications, but just doesn't do anything. This is a typical log of events following
plugin:

Feb 16 20:54:53 mineee nm-system-settings:    SCPlugin-Ifupdown: device added (udi: /org/freedesktop/Hal/devices/usb_device_19d2_31_1234567890ABCDEF_if3_serial_usb_2, iface: (null)): iface not found
Feb 16 20:54:53 mineee NetworkManager: <info>  ttyUSB2: driver is 'usbserial_generic'. 
Feb 16 20:54:53 mineee NetworkManager: <debug> [1234817693.900614] setup_monitor_device(): No monitoring udi provided 
Feb 16 20:54:53 mineee NetworkManager: <info>  Found new Modem device 'ttyUSB2'. 
Feb 16 20:54:53 mineee NetworkManager: <info>  (ttyUSB2): exported as /org/freedesktop/Hal/devices/usb_device_19d2_31_1234567890ABCDEF_if3_serial_usb_2 
Feb 16 20:54:57 mineee NetworkManager: <info>  (ttyUSB2): device state change: 1 -> 2 
Feb 16 20:54:58 mineee NetworkManager: <info>  (ttyUSB2): deactivating device (reason: 2). 
Feb 16 20:54:58 mineee NetworkManager: nm_system_device_flush_ip4_routes_with_iface: assertion `iface_idx >= 0' failed
Feb 16 20:54:58 mineee NetworkManager: nm_system_device_flush_ip4_addresses_with_iface: assertion `iface_idx >= 0' failed
Feb 16 20:54:58 mineee NetworkManager: <info>  (ttyUSB2): device state change: 2 -> 3 

On the odd times that it works, those same entries are immediately followed by an "Activation" entry etc.
and the connection is made. There's no difference in the log entries leading up to that point
between the times it connects and the times it does nothing.

This is NM 0.7 (PPA build 0.7-0ubuntu1~nm1~intrepid1) - not sure what source level that corresponds to.

Any ideas?

Rick Jones