What authentication method are you using? You need to ensure its enabled as a feature of IIS and also ensure that its enabled as an authentication method for your site. I've previously written a blog for enabling Windows authentication on a site but the steps are largely the same for enabling Forms authentication too:
IIS7 comes pretty locked down out the box and you need to explicitly enable each feature you wish to use.
Do you have the EPiServer.Common.Security assembly in the application folder? Which version?
Thank you for posting the link! I'll delve deeper into the problem and mark this thread as a solution if the link helps.
I have EPiServer.Common.Security 2.3.517.36
That seems correct. The reason I asked is that your exception seems to happen when the property tries to create a class from that assembly using reflection. Could it be that you are missing some dependency of that assembly? There are many of them... I think that kind of problem would cause a different type of exception, but who knows... Can you try to install a clean Relate site (if that is what you are using) and compare the assemblies (and perhaps the assembly redirects in web.config)?
We're moving EPiServer from 32-bit IIS 6 to 64-bit IIS 7, but can't get the login to work properly. The error message is as follow:
[NullReferenceException: Object reference not set to an instance of an object.]
EPiServer.Common.Web.Authorization.Integrator.SynchronizeUser(MembershipUser membershipUser, String password, Boolean enableCreateNew) +140
EPiServer.Common.Web.Authorization.Multiplexing.IntegrationMultiplexingMembershipProvider.ValidateUser(String username, String password) +107
System.Web.UI.WebControls.Login.AuthenticateUsingMembershipProvider(AuthenticateEventArgs e) +74
System.Web.UI.WebControls.Login.OnBubbleEvent(Object source, EventArgs e) +123
System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +69
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +28
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2980
If anyone has any suggestion on what's wrong or could point me in the right direction so to speak, I'd appreciate it!