Modemmanager is quite unusable by default, unless user has created custom policykit override configuration that allows access to 'org.freedesktop.ModemManager.Device.Control' action.
Created attachment 303819 [details] modemmanager.pkla
For completeness, org.freedesktop.ModemManager.Contacts, org.freedesktop.ModemManager.SMS, and org.freedesktop.ModemManager.Location should probably also get the same treatment.
Should be fixed in 0.5.2.0. >*modemmanager-0.5.2.0 (27 Mar 2012) > > 27 Mar 2012; Alexandre Rostovtsev <tetromino@gentoo.org> > +files/01-org.freedesktop.ModemManager.pkla, +modemmanager-0.5.2.0.ebuild, > metadata.xml: > Version bump with lots of bugfixes. Allow users in plugdev group full control > over their modems if USE=policykit (bug #406421, thanks to Priit Laes). Add > myself to maintainers.