Comment 13 for bug 1057186

As suggested, I removed 0.6.0.0 version of ModemManager and installed this one ():
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dpkg -s modemmanager
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Package: modemmanager
Status: install ok installed
Priority: optional
Section: net
Installed-Size: 1155
Maintainer: Alexander Sack <email address hidden>
Architecture: amd64
Version: 0.5.1.97-0ubuntu1
Depends: libc6 (>= 2.14), libdbus-glib-1-2 (>= 0.88), libglib2.0-0 (>= 2.31.2), libgudev-1.0-0 (>= 147), upstart-job
Recommends: usb-modeswitch
Conffiles:
 /etc/dbus-1/system.d/org.freedesktop.ModemManager.conf a2a61104bf3fc6aef138de420243f06b
 /etc/init/modemmanager.conf 46dc92ed2060d5db99d5f0c336aaa6f1
Description: D-Bus service for managing modems
 Provides a D-Bus interface to communicate with mobile broadband (GSM, CDMA,
 UMTS, ...) cards. Implements a loadable plugin interface to add work-arounds
 for non standard devices. Also provides patches to use networkmanager (and
 the applet) with modem manager.
 .
 Git Repository: http://cgit.freedesktop.org/ModemManager/ModemManager/
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I rebooted and now everything is working fine.
Thanks @Aleksander for this hint.
Might be a packaging issue for 0.6 version of ModemManager as you said!!!