OK, after a reboot nm-applet got started automatically (via its entry in the Startup Programs) and it works.
I'm still worried about the aforementioned error messages but I had a look at the daemon.log and things seem to be fine. I attached the part of the last login (current one). ** Attachment added: "daemon.log.part" http://launchpadlibrarian.net/12704676/daemon.log.part -- [Hardy] network-manager prevents atheros chip from connecting to the internet https://bugs.launchpad.net/bugs/202453 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
