Failed to open the Group Policy Object -Windows 7 Administrator

Whenever I try to access the Local Group Policy Editor (or access the local security Policy from the Administrative tools folder) I get the following message:

"Failed to open the Group Policy

Object on this computer. You may not
have appropriate rights.

Details: Unspecified Error"

Please can somebody suggest what the problem might be?

I have used a registry cleaner, which might have done the damage.

---

Details

I am using Windows 7 Professional as the Administrator. The PC is freestanding - no domain controller.

Looked in the Administrative Events Log and found plenty of these:

Log Name:      System
Source:        Microsoft-Windows-GroupPolicy

Date:          28/05/2011 23:43:08
Event ID:      1096
Task Category: None
Level:         Error
Keywords:      
User:          Study\The Administrator
Computer:      Study
Description:
The processing of Group Policy failed. Windows could not apply the registry-based policy settings for the Group Policy object LocalGPO. Group Policy settings will not be resolved until this event is resolved. View the event details for more information on the file name and path that caused the failure.
Event Xml:


  
    
    1096
    0
    2
    0
    1
    0x8000000000000000
    

    8415697
    
    
    System
    Study
    
  
  
    2
    1232

    2
    390
    13
    The data is invalid. 
    
    
    LocalGPO
    C:\Windows\System32\GroupPolicy\User\registry.pol
  

Also found loads of these, but don't know if this is relevant:

Log Name:      System
Source:        Microsoft-Windows-DistributedCOM
Date:          28/05/2011 23:37:36
Event ID:      10016
Task Category: None
Level:         Error

Keywords:      Classic
User:          NETWORK SERVICE
Computer:      Study
Description:
The application-specific permission settings do not grant Local Activation permission for the COM Server application with CLSID 
{BC866CF2-5486-41F7-B46B-9AA49CF3EBB1}
 and APPID 
{066FCC09-2096-4EEF-AA2F-353DB80F1BF8}
 to the user NT AUTHORITY\NETWORK SERVICE SID (S-1-5-20) from address LocalHost (Using LRPC). This security permission can be modified using the Component Services administrative tool.
Event Xml:


  
    
    10016
    0
    2
    0
    0
    0x80000000000000
    

    8415679
    
    
    System
    Study
    
  
  
    application-specific
    Local

    Activation
    {BC866CF2-5486-41F7-B46B-9AA49CF3EBB1}
    {066FCC09-2096-4EEF-AA2F-353DB80F1BF8}
    NT AUTHORITY
    NETWORK SERVICE
    S-1-5-20
    LocalHost (Using LRPC)