Why when adding a new portal based on a template I get following error:

Error: Signup is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: Item has already been added. Key in dictionary: "451" Key being added: "451" ---> System.ArgumentException: Item has already been added. Key in dictionary: "451" Key being added: "451" at System.Collections.Hashtable.Insert(Object key, Object nvalue, Boolean add) at System.Collections.Hashtable.Add(Object key, Object value) at DotNetNuke.Entities.Portals.PortalController.ParsePanes(XmlNode nodePanes, Int32 PortalId, Int32 TabId, PortalTemplateModuleAction mergeTabs, Hashtable hModules) at DotNetNuke.Entities.Portals.PortalController.ParseTab(XmlNode nodeTab, Int32 PortalId, Boolean IsAdminTemplate, PortalTemplateModuleAction mergeTabs, Hashtable& hModules, Hashtable& hTabs, Boolean IsNewPortal) at DotNetNuke.Entities.Portals.PortalController.ParseTabs(XmlNode nodeTabs, Int32 PortalId, Boolean IsAdminTemplate, PortalTemplateModuleAction mergeTabs, Boolean IsNewPortal) at DotNetNuke.Entities.Portals.PortalController.ParseTemplate(Int32 PortalId, String TemplatePath, String TemplateFile, Int32 AdministratorId, PortalTemplateModuleAction mergeTabs, Boolean IsNewPortal) at DotNetNuke.Entities.Portals.PortalController.CreatePortal(String PortalName, String FirstName, String LastName, String Username, String Password, String Email, String Description, String KeyWords, String TemplatePath, String TemplateFile, String HomeDirectory, String PortalAlias, String ServerPath, String ChildPath, Boolean IsChildPortal) at DotNetNuke.Modules.Admin.PortalManagement.Signup.cmdUpdate_Click(Object sender, EventArgs e) --- End of inner exception stack trace ---

Error is thrown on this line: hModules.Add(templateModuleID, intModuleId) in components\Portal\PortalController.vb

I dont know why it is trying to add 451 (module id) again in the hashtable. Is there anything wrong that I have done in the database i.e. some names repeated etc due to which it again get 451 module id.