Exchange 2010

Hi Folks
When ever i try to open Exchange 2010 EMC ,am keep on getting this error

" Initialization failed
The  following error occured while searching for the on-premises Exchange Server:
You cannot call a method on a null-valued expression. It was running the command 'Discover-ExchangeServer -UseWIA $true -SuppressError $true -CurrentVersion 'Version 14.3(Build 123.4) "

AND Whenever i try to connect through Exchange PowerShell am getting following errors

" 
VERBOSE: Connecting to INKSG-SVR04.sg.esubstance.com
[] Connecting to remote server failed with the following error message : WinRM cannot proc
ess the request. The following error occured while using Kerberos authentication: A specified logon session does not ex
ist. It may already have been terminated.
 Possible causes are:
  -The user name or password specified are invalid.
  -Kerberos is used when no authentication method and no user name are specified.
  -Kerberos accepts domain user names, but not local user names.
  -The Service Principal Name (SPN) for the remote computer name and port does not exist.
  -The client and remote computers are in different domains and there is no trust between the two domains.
 After checking for the above issues, try the following:
  -Check the Event Viewer for events related to authentication.
  -Change the authentication method; add the destination computer to the WinRM TrustedHosts configuration setting or us
e HTTPS transport.
 Note that computers in the TrustedHosts list might not be authenticated.
   -For more information about WinRM configuration, run the following command: winrm help config. For more information,
 see the about_Remote_Troubleshooting Help topic.
    + CategoryInfo          : OpenError: (System.Manageme....RemoteRunspace:RemoteRunspace) [], PSRemotingTransportExc
   eption
    + FullyQualifiedErrorId : PSSessionOpenFailed
Exception calling "GetComputerSite" with "0" argument(s): "Logon failure: unknown user name or bad password.
"
At C:\Program Files\Microsoft\Exchange Server\V14\bin\ConnectFunctions.ps1:164 char:92
+     $localSite=[System.DirectoryServices.ActiveDirectory.ActiveDirectorySite]::GetComputerSite <<<< ()
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : DotNetMethodException

Exception calling "FindAll" with "0" argument(s): "Unknown error (0x80005000)"
At C:\Program Files\Microsoft\Exchange Server\V14\bin\ConnectFunctions.ps1:253 char:17
+     $search.FindAll <<<< ()
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : DotNetMethodException

You cannot call a method on a null-valued expression.
At C:\Program Files\Microsoft\Exchange Server\V14\bin\ConnectFunctions.ps1:146 char:33
+                 $siteName = $siteDN.ToString <<<< ().SubString(3).Split(",")[0]
    + CategoryInfo          : InvalidOperation: (ToString:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull
"

Any one have any idea why this is happening  or how to sortout this problem

Thanks