Comment 34 for bug 509738

More testing with older and recent modemmanager revealed that the problem is more likely in network-manager:

Non working modem-manager
install modemmanager_0.2.git.20100102t025215.a06b3f2-0ubuntu1~nmt1~karmic_i386.deb
reboot
3G connection not working
install network-manager_0.8~rc1-0ubuntu1~nmt1~karmic_i386.deb
reboot
3G connection working
=======
Non working modem-manager
install self built modemmanager_0.3-0ubuntu1_i386.deb
install network-manager_0.8~rc1-0ubuntu1~nmt1~karmic_i386.deb
reboot
3G connection working
kill switch
3G connection working
=======
Non working modem-manager
install modemmanager_0.3-1ubuntu1+tetet_i386.deb
install network-manager_0.8~rc1-0ubuntu1~nmt1~karmic_i386.deb
reboot
3G connection working
kill switch
3G connection working

All the time the old network-manager had to be installed.