I have installed the latest AD extension. I can log in once. After I try to log in the 2nd time it throws an error:

Method:DotNetNuke.Authentication.ActiveDirectory.AuthenticationController.SynchronizeRoles

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.Authentication.ActiveDirectory.AuthenticationController.SynchronizeRoles(UserInfo objUser)
at DotNetNuke.Authentication.ActiveDirectory.AuthenticationController.AuthenticateUser(UserInfo objUser, ADUserInfo objAuthUser, UserLoginStatus& loginStatus, String ipAddress)
at DotNetNuke.Authentication.ActiveDirectory.AuthenticationController.ManualLogon(String userName, String strPassword, UserLoginStatus& loginStatus, String ipAddress)
at DotNetNuke.Authentication.ActiveDirectory.Login.cmdLogin_Click(Object sender, EventArgs e)
at System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
--- End of inner exception stack trace ---

If I remove the "Sync Groups" option and try to log in it throws this error:

Login Failed. Please remember that passwords are case sensitive