Unknown Error when starting the Group Policy Editor

Question

On Windows 8.1 Professional, I opened the "Edit group policy" from the control panel and also tried to start gpedit.msc from an elevated CMD prompt. In both cases I get the following error message:
In English: Failed to open GPO. You may not have appropriate rights. Details: Unknown Error
There it is again - this dreaded "Unknown Error" message - telling me absolutely nothing about the cause of the problem.
In the past I have been able to launch the GPE on that machine without problems. I can absolutely not remember having messed around with the system files or registry settings. So there is no suspicious thing I could have done to break something. I had a
look at all copies of the GPEDIT.MSC in an editor but none of them looked broken in any way.
I startet C:\WINDOWS\SYSTEM32\MMC.EXE C:\WINDOWS\SYSTEM32\GPEDIT.MSC using the debugger of Visual Studio and paused execution after the error dialog had poped up. I got this call stack:
  gpedit.dll!ReportError(struct HWND__ *,unsigned long,unsigned int,...)    Unknown
  gpedit.dll!CComponentData::Load(struct IStream *)    Unknown
  mfc42u.dll!CWinApp::ProcessShellCommand(class CCommandLineInfo &)    Unknown
I had configured the debugger to break on all exceptions but as you see yourself, MMC is an MFC 4.2 app that doesn't use exceptions.
Since I get no access to the symbols of gpedit.dll, can anybody please tell me which conditions - i.e. problems - in Load() are handled by simply returning E_FAIL? What could be wrong with my machine?

Answer 1

Hi,
Consider the corrupted local policy files and system files, please try these steps:
Step 1: clear local GP by running these commands:
RD /S /Q "%WinDir%\System32\GroupPolicyUsers"
RD /S /Q "%WinDir%\System32\GroupPolicy"
gpupdate /force
Step 2: To scan system files by running this command as admin:
SFC /SCANNOW
Andy error, please post back the CBS.log
Then, restart the computer to check the results.
Also, the event log (Open local event viewer) will show something related to this issue, please check event under
Windows log\Application and Applications and services log\Microsoft\Windows\Grouppolicy, post back if you find any error about this issue.
Kate Li
TechNet Community Support