nm-applet doesn't show an icon if connected using a modem

[flux242]

So if I connect to a wifi access point is shows signal strength as an icon. But if I connect to a 3G network using a USB modem the connection is established and no signal strength icon is displayed. The connection itself is made correctly and works, the nm_applet is still in the panel and can be accessed using right or left mouse button, it just shows no icon but an empty space! It worked perfectly before but after some updated of different packages it stopped working and I'm not sure what could be the reason. I'm using Xubuntu 13.04 but I also tried Xubuntu 13.10 and I have the same problem there.

I also tried to kill the nm-applet process and start it in the console - it shows no warnings or error messages

$ lsb_release -rd
Description: Ubuntu 13.04
Release: 13.04

$ apt-cache policy network-manager-gnome
network-manager-gnome:
  Installed: 0.9.8.0-1ubuntu2
  Candidate: 0.9.8.0-1ubuntu2
  Version table:
 *** 0.9.8.0-1ubuntu2 0
        500 http://de.archive.ubuntu.com/ubuntu/ raring/main amd64 Packages
        100 /var/lib/dpkg/status