I had your same problem and after many attempts resolved it this way:
Finally launch the emulator (if it is the first time you launch it you will have to wait 5-10 minutes, so be patient and wait for it to load all apps it need).
I had the same problem with VisualStudio 2013 Professional and the latest Windows Phone 8.1 SDK and emulators (as of December 2014).
In my case I fixed it by changing the virtual switch 'WinPhoneEmulatorSwitch' in Hyper-V Manager from 'Internal network' to 'Private network'.
I found this solution at pekari.wordpress.com
Open Hyper-V manager. Look at all the emulators that are running and turn them all off.
Then open visual studio and deploy your app.
This will start a fresh instance of Emulator.
I had same problem . first i fixed it with:
But problem came back and instead of previous solution i fixed the issue with :
I solved this problem just now. Please take all windows update. Reboot, and check again for any remaining update. This was a bug earlier as well so microsoft fixed it in first update of windows 8.1
Then check any remaining extension update for your visual studio 2013. update there as well.
Try opening a sample app, it should work.
Regards Kajal