A well-known error message is being thrown from VS 2012 when you try to run the emulator for Windows Phone 8. After you installed all the tools and trying to see your application on the emulator you get the above error and it is a show stopper! It's so frustrating and annoying not to be able to view your running code.
After i was stuck for 3 days, and posting my question in MSDN and contributing on StackOverflow and other forums, all of these suggestions didn't work with me.
My case is fairly simple: I have a brand new laptop, Lenovo AMD E1500 (Supports SLAT) with 4GB RAM on Windows 8 Pro 64bit with VS 2012.
Every time i try to run my windows phone 8 application after selecting "WVGA 512MB" Emulator, it takes forever and i got this error:
Application Deployment Failed, Please try again.
When i check the output window in VS2012, I see the error happens when the VS 2012 tries to connect to the created VM in Hyper-V.
Here is the steps you have to make sure befor uninstalling the SDK or the other tools:
1) Turn off windows firewall.
2) Make sure that you are running VS 2012 as an administrator.
3) Make sure that you are a member of Hyper-V Administrator on your machine.
4) Open Hyper-V and check the you have a VM called "Emulator WVGA 512MB" since this is the VM that VS 2012 is trying to deploy the xap file into.
NOTE: IF YOU DON'T HAVE THE VM, THIS POST IS NOT INTENTED TO FIX IT.
5) Check the connection type for "Windows Phone Emulator Internal Switch" in Hyper-V manager by clicking on Virtual Switch Manager link on the right pane is Internal.
6) In the control panel, Check Network and Sharing Center and then click on change adapter settings --> you should be able to find 3 adapters starts with vEthernet, those are being used with Hyper-V.
Don't change any configuration by your self without any direction from a network guy! missing around these configuration might need you to re-install all the tools and rebuild all virtual switches!
7) Check below Article for MSDN and verify you have the following configuration for "vEthernet (Internal Ethernet Port Windows Phone Emulator Internal Switch)"
8) IMPORTANT: Turn off any antivirus real time scanning, This turns into scanning all communications which slow down the VS/Emulator and times out the emulator running process so you won't be able to deploy your application. THIS WAS MY FINDING AFTER SPENT 3 DAYS!
After following all above instructions you shouldn't have any issues with running your WP8 Emulator.