Windows phone emulator not working (visual studio version 3)?

2 days ago I installed Visual Studio 3 update using select all on windows 8.1 proX64. Yesterday and the day before yesterday, the emulator was working fine, but since this morning, it doesn't work and shows about 4-5 minutes and automatically shuts down the VM, but when I start the VM from hyper-v manager then it works fine. I installed XAMARIN studio this morning .

Windows OS OS starts up .....

http://i.picresize.com/images/2014/11/08/G2q50.png It does not freeze, i.e. Rotation, works. It runs for over ten minutes, after which visual studio gives the following error messages.

Error 1 Error: DEP6100: The following unexpected error occurred during the Upgrade Phase "Connecting to Device": Utility SmartDeviceException - Application crashed. Please try again.
Error 2 Error: DEP6200: Boostrapping 'Emulator 8.1 WVGA 4 inches 512 MB' failed. The device could not be found. Application deployment failed. Try again.

I've tried the following methods, but none of them work.
After closing visual studio
1. Remove the entire virtual machine from Hyper-v manager and remove the switch from virtual mastton manager and restart PC and Visual studio.
2. Restore the Windows Phone Emulator from Control Panel, uninstall or change the program, and restart your computer.
3. Direct launch from Hyper-v manager.
4. Unistalling and installing Windows Phone SDK. Restart Windows OS

How do I fix this error?