Unable to determine the page link

I am using Zen Cart 1.3.8 and having this error "Unable to determine the page link".

How to reproduce my configuration:

• Set the catalog to be visible only to registered and approved customers
• Visit the catalog, you should see a login form
• Login as an existing and approved customer
• You should now see the catalog
• Now enter the administration at http://your.store.com/admin
• After logging in just log out

At this point I have the error "Unable to determine the page link" on the page.

As I saw it's due to "zenid" cookie, in fact I solved inserting this row at the beginning of /admin/login.php (before everything):

setcookie ("zenid", "", time() - 3600, "/", ".".$_SERVER["HTTP_HOST"]);

In this way the cookie is deleted after logging out the backoffice.

Devis Lucato