Why is the (Mac OS X) android emulator network disconnected?

I have a number of different Android Virtual Devices. Sometimes when I launch them the network connec开发者_StackOverflow社区tion for the virtual device doesn't work. The network bar box on the top status bar will show up with an 'x' in it. Recently this has been happening more often than not. Why is it that the virtual device network sometimes not work?

Also, when I use the settings app and go to "wi-fi" the checkmark is off and if I click on it I get the "error" message, but no more details than that.

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On OS X the network device that is listed in the Network preferences panel on top seems to be taken for network connectivity.

I recently had the case that I was on wireless (Airport, en1) , while en0 was still marked as up (but no cable connected). So en0 was found before en1 and the emulator did not have networking even as browser, email etc. itself worked nicely. Shutting down en0 immediately solved the issue.