Samsung SGH-Z810 dongle does not work after the first insertion

I am trying to use a USB modem (dongle) Samsung SGH-Z810. (It is a GSM device serving to connect to a 3G mobile broadband network in my case).

How can I reproduce the bug:
1.) I start the computer (a HP ZBook 15 notebook).

2.) Once the system (64-bit ubuntu) is running and I am logged in I wait for say 10 seconds and then insert the modem into a USB port. Nothing happens. NetworkManager does not list this networking option even after another period of waiting.

3.) I unplug the modem and after a while I insert it again. FInally I can see the networking option listed in the NetworkManager menu and I can connect.

Even this has to be done manually although I asked for automatic connection in the NetworkManager settings.

Other way to start the computer is to do it with the modem inserted in a USB port. If I do it the problem is the same: I have to unplug the dongle and reinsert it before I can start networking.

The computer seemingly randomly chooses to display or not to display the device folder in a File Manager item.

I experience similar issues also with a different USB modem: HUAWEI E3251. The difference is that this one at least connects automatically. It is formally seen as an ethernet device though.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: modemmanager 1.0.0-2
ProcVersionSignature: Ubuntu 3.13.0-8.28-generic 3.13.2
Uname: Linux 3.13.0-8-generic x86_64
ApportVersion: 2.13.2-0ubuntu4
Architecture: amd64
CurrentDesktop: Unity
Date: Mon Feb 17 06:58:31 2014
InstallationDate: Installed on 2014-01-31 (16 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140130)
SourcePackage: modemmanager
UpgradeStatus: No upgrade log present (probably fresh install)