2
Open checklogin.php in the includes folder, look for:
if (!$allowed) {redirect_header(XOOPS_URL.'/index.php', 1, _NOPERM);exit();
(this should be line 70)
Change '/index.php' to the page you want to redirect to.
Make a backup of this file incase you have problems, I did this and it worked for me but backup original file is a good thing