1.4.0 is written for phpBB 3.0.5. I have repackaged it and have sent it to the phpbb.com MODDB just some days ago.
IMO it woul dbe better to install 1.4.0 insteat of 1.0.9. Im not running 1.0.9 on any of my boards. So I can't support it really.
Do you know this post: http://www.phpbb.com/community/viewtopi ... 5#p4231435
Just look again to the includes/ucp/ucp_register.php . I think the failure is located here. There in this file should not be a big difference between 1.0.9 and 1.4.0. If you want just send me this file per e-mail. I will have a look to it.