Cannot Install Exchange 2013 on Windows 2012 DC Server!?

Hi,

when i try to install my Exchange 2013 on a Windows 2012 Server i become the following error at the Transport Service Tab:

Error:
The following error was generated when "$error.Clear();
          $maxWait = New-TimeSpan -Minutes 8
          $timeout = Get-Date;
          $timeout = $timeout.Add($maxWait);
          $currTime = Get-Date;
          $successfullySetConfigDC = $false;

          while($currTime -le $timeout)
          {
            $setSharedCDCErrors = @();
            try
            {
              Set-SharedConfigDC -DomainController $RoleDomainController -ErrorVariable setSharedCDCErrors -ErrorAction SilentlyContinue;
              $successfullySetConfigDC = ($setSharedCDCErrors.Count -eq 0);

              if($successfullySetConfigDC)
              {
                break;
              }
              Write-ExchangeSetupLog -Info ("An error ocurred while setting shared config DC. Error: " + $setSharedCDCErrors[0]);
            }
            catch
            {
              Write-ExchangeSetupLog -Info ("An exception ocurred while setting shared config DC. Exception: " + $_.Exception.Message);
            }

            Write-ExchangeSetupLog -Info ("Waiting 30 seconds before attempting again.");
            Start-Sleep -Seconds 30;
            $currTime = Get-Date;
          }

          if( -not $successfullySetConfigDC)
          {
            Write-ExchangeSetupLog -Error "Unable to set shared config DC.";
          }
        " was run: "Unable to set shared config DC.".