When trying to create a user, I'm getting an "Object reference not set to an instance of an object" error.  With nothing in the inner exception, I'm not sure what I'm missing, since the exception isn't giving any details.  Inspecting the MembershipProvider.Instance() looks good, with not exceptions. 

            var userInfo = new UserInfo();
            userInfo.Profile.InitialiseProfile(0);
            userInfo.DisplayName = string.Format("{0} {1}", this.FirstName, this.LastName).Trim();
            userInfo.Email = this.Email;
            userInfo.FirstName = this.FirstName;
            userInfo.LastName = this.LastName;
            userInfo.PortalID = 0;
            userInfo.Username = this.UserName;
            userInfo.IsSuperUser = false;         
            userInfo.Membership.Password = this.Password;
            userInfo.Membership.CreatedDate = DateTime.Now;
            userInfo.Membership.UpdatePassword = false;
            userInfo.Membership.Approved = true;

   UserCreateStatus status = MembershipProvider.Instance().CreateUser(ref userInfo);
            

 

 

I got this from the Logs...

2014-02-12 15:10:15,737 [ASPNET2-PC][Thread:62][ERROR] DotNetNuke.Services.Exceptions.Exceptions - System.NullReferenceException: Object reference not set to an instance of an object.
   at DotNetNuke.Security.Membership.AspNetMembershipProvider.CreateUser(UserInfo& user)
   at Foundation.Portal.Modules.DonorPreferences.SecurityService.SaveUser(User user, Int32 roleId) in c:\inetpub\wwwroot\dotnetnuke\DesktopModules\DonorPreferences\SecurityService.svc.cs:line 33

Thanks for the reply. I found the link you sent, a couple of days ago. Still getting the "object not set" error. I wish the DNN dll would give a better exception. I'll step through the application's source code to see what it is doing differently...