Debian 7 (wheezy) - mobile broadband support in NetworkManager unstable

[Phil Reynolds <phil-nm tinsleyviaduct com>]

It never has been very stable, but in recent weeks I've noticed that
NetworkManager is very unstable when it comes to my mobile connection.

I am using Debian wheezy (the stable release) on a Lenovo Thinkpad
X131e, fitted with the Ericsson H5321 3G modem, and an Andrews & Arnold
(www.aa.net.uk) data SIM.

I see a variety of symptoms, but basically they boil down to:

o       Connection is dropped, and disappears from NetworkManager's
        menu, only to be replaced by "Auto broadband", which doesn't
        work. Restarting NetworkManager usually helps in this case.

o       Connection is dropped, and cannot be restored because the
        Mobile Broadband switch in the menu will not stay on. Often,
        restarting NetworkManager helps, but sometimes a reboot seems
        to be needed.

Is there anything I can do to make this situation more stable?

-- 
Phil Reynolds
mail: phil-nm tinsleyviaduct com