I just wanted to say that I managed to get past the cert error that you're talking about. Basically, I followed the following steps:
- Load up PowerShell as Adminstrator.
- Type 'Show-WindowsDeveloperLicenseRegistration'.
- It will prompt you for you Live ID so just type that in.
- Next, run 'Set-ExecutionPolicy unrestricted'.
- Now, from within the MetroClient_1.7.0.0_AnyCPU_Test folder, run the 'Add-AppDevPackage.ps1' file.
This will install the required certificate and stick the application on the Start Screen. Hope this helps.