Method 1:
Close all MMC/EMC instances before proceeding. Open Registry Editor (regedit) as the user you run the EMC under. Go to HKEY_CURRENT_USER\SOFTWARE\Microsoft\ExchangeServer\v14\AdminTools Look for value NodeStructureSetting. If it is there, back it up and then remove it.
Method 2:
Close all MMC/EMC Instances before proceeding. Open Powershell or Powershell IDE as the user you run the EMC under and execute the following command: Remove-ItemProperty -Path HKCU:\Software\Microsoft\ExchangeServer\v14\AdminTools\ -Name NodeStructureSettings Close Powershell