I've run into this exact same issue with modemmanager 1.0.0-2ubuntu1 running Linux Mint 17.1. Downgraded to 0.5.2.0-0ubuntu2, and the modem works as specified and is stable.
** Attachment added: "log" https://bugs.launchpad.net/ubuntu/+source/modemmanager/+bug/1390769/+attachment/4302021/+files/log -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1390769 Title: modemmanager breaks Pantech UML295W Ubuntu 14.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/modemmanager/+bug/1390769/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs