Hello. I just recently upgraded to 5.2.1 and now after any user logs in it throws the following error:

A critical error has occurred.
Object reference not set to an instance of an object.

The page loads (displays the error inline, but all other features & functions are fine) and the event viewer shows that the login occurred successfully. This error does not display on the page during subsequent page loads - only after login.

If anyone can provide any insight I would really appreciate it. I have searched through these forums, google, bing - everywhere I can think of - to find a solution. All to no avail.

Here is the stack trace:

AssemblyVersion: 5.2.1
PortalID: 0
PortalName: My Collaboration Portal
UserID: -1
UserName:
ActiveTabID: 327
ActiveTabName: Home
RawURL: /dotnetnuke/Default.aspx?tabid=327&ctl=Login&returnurl=%2fdotnetnuke%2fDefault.aspx%3ftabid%3d327
AbsoluteURL: /dotnetnuke/Default.aspx
AbsoluteURLReferrer: /dotnetnuke/Default.aspx?tabid=327&ctl=Login&returnurl=%2fdotnetnuke%2fDefault.aspx%3ftabid%3d327
UserAgent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 1.0.3705; Media Center PC 4.0; .NET CLR 3.0.04506.30; InfoPath.2; MS-RTC LM 8; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: 728fe185-58b1-4270-bef5-e13564c1ed58
InnerException: Object reference not set to an instance of an object.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: DotNetNuke.Common.Utilities.XmlUtils.GetAttributeValueAsInteger
StackTrace:
Message: DotNetNuke.Services.Exceptions.PageLoadException: Object reference not set to an instance of an object. ---> System.NullReferenceException: Object reference not set to an instance of an object. at DotNetNuke.Common.Utilities.XmlUtils.GetAttributeValueAsInteger(XPathNavigator nav, String AttributeName, Int32 DefaultValue) at DotNetNuke.Common.Utilities.Config.GetPersistentCookieTimeout() at DotNetNuke.Entities.Users.UserController.UserLogin(Int32 portalId, UserInfo user, String PortalName, String IP, Boolean CreatePersistentCookie) at DotNetNuke.Modules.Admin.Authentication.Login.ValidateUser(UserInfo objUser, Boolean ignoreExpiring) at DotNetNuke.Modules.Admin.Authentication.Login.UserAuthenticated(Object sender, UserAuthenticatedEventArgs e) at DotNetNuke.Services.Authentication.AuthenticationLoginBase.OnUserAuthenticated(UserAuthenticatedEventArgs ea) at DotNetNuke.Modules.Admin.Authentication.Login.cmdLogin_Click(Object sender, EventArgs e) at System.Web.UI.WebControls.Button.OnClick(EventArgs e) at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception stack trace ---
Source:
Server Name: My-DNN-SERVER

Hi Ken. Thanks for the response.

We actually run DNN in several different environments - some self hosted and others hosted on GoDaddy. The portals (parent and all child portals) where we experienced the problem were self hosted. I have not yet identified the specific cause of the error, but I was able to fix it. I noticed a backup copy of the web.config file with a date/time stamp after the upgrade (definitely after the upgrade completed but before the problems arose) in the root directory. I restored that web.config  and all subsequent logins have been successful. It is unclear where this backup web.config file came from. It was named like a file from a system or database backup; i.e web.config.01152010023645.bu. Our backup devices are not setup to place files anywhere but the removable drives. Strange.

Hopefully in the next day or so I will have an opportunity to compare the 2 web.config files to see what changed. I will update my post with the details so anyone else experiencing the problem will know where to look.

Thanks again for the response.

After a lot more searching I found a post relation to 'location'

I removed the following redirection from my web.config file and that fixed the problem for me...

    <!--
    <location path="purchase.html">
        <system.webServer>
            <httpRedirect enabled="true" destination="http://www.mycourts.com.au/purchase.aspx" exactDestination="true" httpResponseStatus="Permanent" />
        </system.webServer>
    </location>
    <location path="download.html">
        <system.webServer>
            <httpRedirect enabled="true" destination="http://www.mycourts.com.au/downloads.aspx" exactDestination="false" httpResponseStatus="Permanent" />
        </system.webServer>
    </location>
        -->

The other post mentioned the path was incorrect so I will try to play with that so that I can redirect again but at least I have fixed the DNN issue.