I'm trying to upgrade version 4.07 to 4.09.02 on a production server.  The server is running Windows 2003 and SQL Server 2000.  When I follow the upgrade procedures, using the upgrade package, the upgrade runs with no errors.  However, when I then try to go in to the site I'm getting this ArgumentNullException stack error.  The stack trace is:

[ArgumentNullException: Value cannot be null.
Parameter name: replacement]
   System.Text.RegularExpressions.Regex.Replace(String input, String replacement, Int32 count, Int32 startat) +5259975
   System.Text.RegularExpressions.Regex.Replace(String input, String replacement) +38
   System.Text.RegularExpressions.Regex.Replace(String input, String pattern, String replacement, RegexOptions options) +47
   DotNetNuke.UI.Skins.SkinController.formatSkinSrc(String SkinSrc, PortalSettings PortalSettings) +123
   DotNetNuke.Entities.Portals.PortalSettings.GetPortalSettings(Int32 TabId, PortalAliasInfo objPortalAliasInfo) +3480
   DotNetNuke.Entities.Portals.PortalSettings..ctor(Int32 tabId, PortalAliasInfo objPortalAliasInfo) +77
   DotNetNuke.Common.Globals.GetHostPortalSettings() +156
   DotNetNuke.Common.Globals.GetPortalSettings() +82
   DotNetNuke.Authentication.ActiveDirectory.HttpModules.AuthenticationModule.Init(HttpApplication application) +198
   System.Web.HttpApplication.InitModulesCommon() +65
   System.Web.HttpApplication.InitModules() +43
   System.Web.HttpApplication.InitInternal(HttpContext context, HttpApplicationState state, MethodInfo[] handlers) +729
   System.Web.HttpApplicationFactory.GetNormalApplicationInstance(HttpContext context) +298
   System.Web.HttpApplicationFactory.GetApplicationInstance(HttpContext context) +107
   System.Web.HttpRuntime.ProcessRequestInternal(HttpWorkerRequest wr) +289
 

I can re-run the install command and for awhile the site will work.  However, as soon as I go to add a module through the Module Definitions page the site stops with the above errror.  After running a hour or two the site will stop with the above error.  If I re-run the install command the error goes away.  I've made sure the Network Services security entity has full control over the files & directories.  My database version is now 4.09 and the DotNetNuke version is listing as 4.09.02.  I can roll the site back to version 4.07 and it works all the time.  I cannot get past this issue.