Manage Access Rules Error

Everything else is working fine.  Except when I clickon Manage Access Rules, I keep getting this error:
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.InitForConfiguration(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.InternalConfigConfigurationFactory.System.Configuration.Internal.IInternalConfigConfigurationFactory.Create(Type typeConfigHost, Object[] hostInitConfigurationParam ...