I have tried to create the document for EMC not opening issue it contain major steps which we take to fix the issue. All the steps are along with screen shots hope this will help.
Make sure all the prerequisite are installed while installing CAS role: Exchange 2010 Prerequisites
Follow the Link Troubleshooting Exchange 2010 Management Tools startup issues
Check following entries in applicationhost.config file under GlobalModules (c:\windows\system32\inetsrv\config) Note: Path is subject to Installation in the environment.
NOTE: path for kerbauth depend on the installation folder of Exchange also make a copy of original file as a backup.
<add name=”kerbauth” image=”C:\Program Files\Microsoft\Exchange Server\V14\Bin\kerbauth.dll” />
<add name=”WSMan” image=”C:\Windows\system32\wsmsvc.dll” />
Once you add above entry restart the IISADMIN service using services console and run IISRESET.
Now open up the IISMANAGER and goto (Default Web Site->PowerShell->Modules) and click on Configure Native Modules… under Actions right side.
Go to (Default Web Site->PowerShell->Modules) and click on Configure Native Modules… under Actions right sideOnce you add above in the powershell module go back to server modules select kerbauth+WSMan and click remove.
Try open the EMC and if you do not get above response or you are still unable to open the EMC
Replace the web.config file for the PowerShell with the default file attached to the email as I have taken the backup of Web.config file of PowerShell and the whole config folder (c:\windows\system32\inetsrv\config). Note: PLEASE take the backup of original file before making any changes/replacing file.