Comment 8 for bug 566812

The problem is that when a device switches from any state besides the final CONNECTED state to the FAILED state, networkmanager marks the connection as invalid to avoid it from reconnecting over and over. However, this behavior is not sane when the connection type is mobile broadband, as the intermediate states have no meaning, as they are not informed by the modem. So the sane behavior is to let networkmanager reconnect and let the user to unplug the modem or "disable mobile broadband" if desired.

The attached patch was tested applied against network-manager 0.8.2-0ubuntu1~nmt2 from ppa:network-manager/ppa in maverick, and solved the issue, allowing to reconnect without hacks after pppd hanged up, and even to setup networkmanager to reconnect automatically (just set the connection as automatic).