Sadly, the patch from the launchpad bug report doesn't solve the issue for me. Network-manager gets a bit better in that it actually tries to reconnect but modem-manager still seems to go into a coma sometimes (fixed by killing modem-manager which is autostarted again).
-- David Härdeman -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org