I have used this modem (huawei EC 1260-2) since ubuntu 12.04 untill 13.10 and it runs fine. But with ubuntu 14.04. nm-applet detects my modem but cannot establish the connection. My configuration was correct.
Below I will explain further information, the correlation between nm-applet and mobile partner (huawei gui)
The chronology:
1. Plug the modem and then network-manager (nm) detects my modem.
(I have set up the configuration and rebooted before) I'm trying to establish the connection.
2. The nm-applet shows it's trying to establish the connection, but the modem LED is still blinking slowly like it hasn't established the connection. (Blinking faster are indicating that the modem is trying to establishes the connection)
3. After that I install Mobile Partner (which I used on my Ubuntu 12.04 and 13.10) and the installations were successful, reboot my PC as usual.
4. Then I'm trying to plug in the modem again and network-manager applet detects my modem, Mobile Partner displays its window.
5. Then a dialog from Mobile Partner suddenly automatically appears that says: "the device has been disconnected or unavailable", no signal was detected and the 'connect' button is grayed out.
6. But the network-manager still shows the detection of my modem. OK, trying to connect through network-manager, but like before it fails.
The correlations are:
1. Mobile Partner says my modem is disconnected, but network manager still detects my modem, but cannot establish the connection. In my previous version of Ubuntu, when I unplugged my modem, Mobile Partner said: the device has been disconnected or unavailable and the network-manager did not detect my modem.
2. But now in Ubuntu 14.04 beta 2, I did not unplug my modem and Mobile Partner says: the device has been disconnected or unavailable and network manager still detects my modem, but cannot establish the connection.
3. As usual, when trying to establish the connection, the modem LED indicator is blinking faster, but now doesn't like that (It means that there are no activity on modem while nm-applet show it trying to connect).
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: modemmanager 1.0.0-2ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-23.45-generic 3.13.8
Uname: Linux 3.13.0-23-generic i686
NonfreeKernelModules: wl
ApportVersion: 2.14.1-0ubuntu2
Architecture: i386
CurrentDesktop: Unity
Date: Sat Apr 12 08:19:21 2014
InstallationDate: Installed on 2014-04-07 (4 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Beta i386 (20140326)
SourcePackage: modemmanager
UpgradeStatus: No upgrade log present (probably fresh install)
Status changed to 'Confirmed' because the bug affects multiple users.