Hi,
    I am Kapil Samadhiya. I am facing this problem in accessing my DotNetNuke site. I am using DotNetNuke-4.5.3 version. Earlier my site was running, but its stopped running suddenly and giving this error. May be it is because of uploading any new module, But I have tried after removing DLLs of that module. Still site is not running.

I am also confused because its giving error of "Object reference not set to an instance of an object.

Source Error:

[NullReferenceException: Object reference not set to an instance of an object.]
   DotNetNuke.Entities.Portals.PortalSettings.VerifyPortalTab(Int32 PortalId, Int32 TabId) +320
   DotNetNuke.Entities.Portals.PortalSettings.GetPortalSettings(Int32 TabId, PortalAliasInfo objPortalAliasInfo) +2413
   DotNetNuke.Entities.Portals.PortalSettings..ctor(Int32 tabId, PortalAliasInfo objPortalAliasInfo) +83
   DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +2677
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64

" while accessing through localhost, But If I am accessing this site from outside (internet) then its giving error of "Runtime Error"

Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.

Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customErrors> tag within a "web.config" configuration file located in the root directory of the current web application. This <customErrors> tag should then have its "mode" attribute set to "Off".

<!-- Web.Config Configuration File -->

<configuration>
    <system.web>
        <customErrors mode="Off"/>
    </system.web>
</configuration>

<!-- Web.Config Configuration File -->

<configuration>
    <system.web>
        <customErrors mode="RemoteOnly" defaultRedirect="mycustompage.htm"/>
    </system.web>
</configuration>

Did you mean that I need to save a blank web.config in root directory and then try to access the application?

I have the same problem. WHO CAN HELP ME OUT?

I had a working DNN-site and had added pages etc and all was working fine for a couple of months.

Yesterday i wanted to add some articles. So I logged in, added a new page. That adding went strange. I could not access the new page, then it appeared twice, when I tried to add a module to it, it did so but the module did not show. A bit later the module showed but when I tried to enter its settings, it said it was not there.

Then I could not change the settings of the page anymore.

I tried to delete the page, it said it had deleted it, but when I checked the menu of [pages], it was still there.

Then it seemed my homepage had gone. When I went to the homepage of my site www. veiligenzuinig.nl in a fresh browser-window, it gave the error below:

Object reference not set to an instance of an object.

[NullReferenceException: Object reference not set to an instance of an object.]
   DotNetNuke.Entities.Portals.PortalSettings.VerifyPortalTab(Int32 PortalId, Int32 TabId) +404
   DotNetNuke.Entities.Portals.PortalSettings.GetPortalSettings(Int32 TabId, PortalAliasInfo objPortalAliasInfo) +2413
   DotNetNuke.Entities.Portals.PortalSettings..ctor(Int32 tabId, PortalAliasInfo objPortalAliasInfo) +83
   DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +2677
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64

When I try to access another page of the site, that works. The page is shown. But when I try to change something, strange things occur.

I decided to give it a rest and see again today.

Today, it even seems worse.

I can not reach the homepgae, I get the above error.

I can reach another page, but when i try to log-in, it does not work. I again get the similar error as above:

Object reference not set to an instance of an object.

[NullReferenceException: Object reference not set to an instance of an object.]
   DotNetNuke.Entities.Portals.PortalSettings.VerifyPortalTab(Int32 PortalId, Int32 TabId) +404
   DotNetNuke.Entities.Portals.PortalSettings.GetPortalSettings(Int32 TabId, PortalAliasInfo objPortalAliasInfo) +2413
   DotNetNuke.Entities.Portals.PortalSettings..ctor(Int32 tabId, PortalAliasInfo objPortalAliasInfo) +83
   DotNetNuke.HttpModules.UrlRewriteModule.OnBeginRequest(Object s, EventArgs e) +2677
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64

*   I tried to 'restart' the application by changing something in the config-file. The application did restart, but then it still did not go.

Who can help me out?