Error in Web Site Administration Tool

[Shimon Sim]

I have following error when I try to "Manage access rules". I am using my
role provider and wanted to know if this could be caused by my code.
Thanks.
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An error was encountered. Please return to the previous page and try again.

The following message may help in diagnosing the problem: Specified argument
was out of the range of valid values. Parameter name: site at
System.Web.Configuration.WebConfigurationHost.Init ForConfiguration(String&
locationSubPath, String& configPath, String& locationConfigPath,
IInternalConfigRoot configRoot, Object[] hostInitConfigurationParams) at
System.Configuration.Configuration..ctor(String locationSubPath, Type
typeConfigHost, Object[] hostInitConfigurationParams) at
System.Configuration.Internal.InternalConfigConfig urationFactory.System.Configuration.Internal.IInte rnalConfigConfigurationFactory.Create(Type
typeConfigHost, Object[] hostInitConfigurationParams) at
System.Web.Configuration.WebConfigurationHost.Open Configuration(WebLevel
webLevel, ConfigurationFileMap fileMap, VirtualPath path, String site,
String locationSubPath, String server, String userName, String password,
IntPtr tokenHandle) at
System.Web.Configuration.WebConfigurationManager.O penWebConfigurationImpl(WebLevel
webLevel, ConfigurationFileMap fileMap, String path, String site, String
locationSubPath, String server, String userName, String password, IntPtr
userToken) at
System.Web.Configuration.WebConfigurationManager.O penMappedWebConfiguration(WebConfigurationFileMap
fileMap, String path) at
System.Web.Administration.WebAdminPage.OpenWebConf iguration(String path,
String appPhysPath, Boolean getWebConfigForSubDir) at
System.Web.Administration.WebAdminPage.OpenWebConf iguration(String path,
Boolean getWebConfigForSubDir) at
ASP.security_permissions_managepermissions_aspx.Bi ndGrid() at
ASP.security_permissions_managepermissions_aspx.Pa ge_Load() at
System.Web.Util.CalliHelper.ArglessFunctionCaller( IntPtr fp, Object o) at
System.Web.Util.CalliEventHandlerDelegateProxy.Cal lback(Object sender,
EventArgs e) at System.Web.UI.Control.OnLoad(EventArgs e) at
System.Web.UI.Control.LoadRecursive() at
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint,
Boolean includeStagesAfterAsyncPoint)