why is registry access denied - 'System.Security.SecurityException' in mscorlib.dll

[starrysky]

Trying to read key "HKLM\SOFTWARE\Policies\Microsoft\Windows\WindowsU pdate\AU" value "AUOptions"

and get the following :
A first chance exception of type 'System.Security.SecurityException' occurred in mscorlib.dll
Error occurs in ReadRegistry key SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\ AU : Requested registry access is not allowed.

This occurs in my vb.net application when application is run under an account called OPER in the USERS group. The application :
1/is on my PC's hard drive, its not a web app or on a network share
2/is launched via a desktop click
3/ has a manifest specifying executionlevel "AsInvoker"

It does not occur when the Application is run as an Administrator. It does not occur if I read the value with a non .NET program when logged in as OPER whch makes me think it is a .NET problem not a registry permissions problem.
Examining "Effective Permissions" shows that my OPER login has query value permission.

I need the application to be able to read the key like the non .NET application while running at USERS level. Anyone any ideas what the problem is please?

[starrysky]

Apologies for posting original message, silly mistake- I have cracked this myself

I had opened the registry subkey requesting write access
Key = ParentKey.OpenSubKey("SOFTWARE\Policies\Microsoft\ Windows\WindowsUpdate\AU", true)

And so it was denied - I needed it to be read only
Key = ParentKey.OpenSubKey("SOFTWARE\Policies\Microsoft\ Windows\WindowsUpdate\AU", False)