First kill the network-manager applet.
Originally Posted by CoyoteUK5
Now make sure your network-manager service is running.
$ sudo killall nm-applet
Now start nm-applet again: press ALT-F2 and enter this command:
$ sudo /etc/init.d/network-manager start
$ sudo service network-manager start
If you network ESSID isn't showing, then you may have a driver issue. In this case, type
into the terminal. Copy and paste all the output into a new reply in this thread, and I'll see what I can do from there.