This is definitely a problem with Mail Servers. Please set proper SMTP Settings and mail address. If the registration still doesn’t work, tweak a few lines of code in ManageUsers.ascx.vb which is under DesktopModules/Admin/Security Folder. It registers the user correctly but the error occurs in sending mail in UserCreateCompleted Method where

strMessage = CompleteUserCreation(e.CreateStatus, e.NewUser, e.Notify, IsRegister)

 In CompleteUserCreation Function

Case PortalRegistrationType.PublicRegistration

Mail.SendMail(newUser, MessageType.UserRegistrationPublic, PortalSettings)

Dim loginStatus As UserLoginStatus

UserController.UserLogin(PortalSettings.PortalId, newUser.Username, newUser.Membership.Password, "", PortalSettings.PortalName, "", loginStatus, False)

The Mail.SendMail throws an error because of which the two lines below the Mail.SendMail which logs you into the website isnt executed.

Please take a backup of your ManageUsers.ascx.vb. Browse to the following URL and copy all the lines of code and replace the whole code in your ManageUsers.ascx.vb.

http://www.europeanstopovers.com/Mana...

The Registration in DNN 5.6 worked for me. Hope it works for you too.

I installed DotNetNuke 6.0 CTP Edition and registration seems to work fine. So I hope with 6.0 there wont be any problems with registration in the future.

Thank you! This fixed my problem! I was getting errors registering, adding, and modifying user accounts. 

I recently removed thousands of spam accounts and accidentally changed my portal admin (to a user with a different email address than the Super User account and the account used to configure my SMTP settings). 

I changed the portal admin account back to the way it was and all my errors stopped!

Thanks again!