That was a good guess, not 100% right though
I am connected to a wifi net, the computer has also an eth interface - enabled, but not connected to anything. Running NetworkManager from ubuntu repos.
1. If I just "disconnect" using the applet, behaviour is as I showed first. The OS sees both eth0 and wlan interfaces, but there is no ip assigned to any of them. The routing table is empty
2. If I unplug my wifi router, same deal
3. If I plug in my wifi router but disconnect it from the modem, behaviour is as should be. In other words, things work ok when the computer is actually connected to a network.