Ok that is different to what I have, I see you have an auto login hack. The lines in blue you have included are different to mine, I am lost now lol. this is what I have in my read_me file, well two steps that I have that are similar to that blue highlight
#################################################
Modify <xoops_root>/user.php
#################################################
-Find
redirect_header('user.php',5,_US_ACTLOGIN);
or
redirect_header( 'user.php', 5, _US_ACTLOGIN, false );
-Add theses 2 lines just above:
require_once XOOPS_ROOT_PATH . '/modules/mpmanager/include/functions.php';
mpauto($id);
#################################################
Modify <xoops_root>/register.php
#################################################
-Find:
redirect_header('index.php', 4, _US_ACTLOGIN);
-Add theses 2 lines just above:
require_once XOOPS_ROOT_PATH . '/modules/mpmanager/include/functions.php';
mpauto($newid);
Maybe we have a different version, or have you changed it for your own situation, am I missing something, I don't see checklogin.php mentioned is that part of the autologin hack lol. Maybe I am on the wrong page (cognitive functions aint so good these days) ;o) Hopefully someone else can help, Good luck and I am glad you got back into your site.
I am so lost what version of XOOPS are you using? Anyway I am off to the land of nod. Cheers.