ASP.Net 3.5 Ch13, Securing Your Web Application

I am trying to follow the book in a programming class I am running. I am following the text and on page 583 I am told I can create access rules for visitors of the Dorknozzle site. I have created two users and two roles. When I go to assign access rules I selected the Dorknozzle site (~/someDirectory/…/dorknozzle)* and assign anonymous users to “deny”; admin has access. This all works well and good on the site. The problem is with the Web Site Administration Tool.

I want to create and manage other users. When I go to the Web Site Administration Tool I get the following message:

[INDENT]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 hostInitConfigurationParams) at System.Web.Configuration.WebConfigurationHost.OpenConfiguration(WebLevel webLevel, ConfigurationFileMap fileMap, VirtualPath path, String site, String locationSubPath, String server, String userName, String password, IntPtr tokenHandle) at System.Web.Configuration.WebConfigurationManager.OpenWebConfigurationImpl(WebLevel webLevel, ConfigurationFileMap fileMap, String path, String site, String locationSubPath, String server, String userName, String password, IntPtr userToken) at System.Web.Configuration.WebConfigurationManager.OpenMappedWebConfiguration(WebConfigurationFileMap fileMap, String path) at System.Web.Administration.WebAdminPage.OpenWebConfiguration(String path, String appPhysPath, Boolean getWebConfigForSubDir) at System.Web.Administration.WebAdminPage.OpenWebConfiguration(String path, Boolean getWebConfigForSubDir) at ASP.security_permissions_managepermissions_aspx.BindGrid() at ASP.security_permissions_managepermissions_aspx.Page_Load() at System.Web.Util.CalliHelper.ArglessFunctionCaller(IntPtr fp, Object o) at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(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)[/INDENT]

The systems is running Windows Server 2003 R2, IIS 6.0.
*We are also using virtual directories to manage the multiple sites. I have one server with a number of students logging in to develop multiple projects for various classes. The directory structure would be ~/studentName/course/project(i.e. Dorknozzle)

Thanks in advance for your help.