Comment # 1 on bug 901122 from Dominique Leuenberger

To not loose all the information that was passed on the mailing listn continued
from http://lists.opensuse.org/opensuse-gnome/2014-10/msg00023.html

there seems to be a firmware issue in some cdc devices, that do not get reset
properly after a reboot.

We can try to add a restart-script in /usr/lib/systemd/system-sleep

50-restart_MM
>>> - SNIP HERE  - <<<
#!/bin/sh 
case $1 in
    resume|thaw|post)
        /usr/bin/systemctl restart ModemManager.service > /dev/null
    ;;
esac
>>> - SNIP HERE - <<<

Can you please verify if that helps you in any way?