since a wile each time a customer wants to log in, the customer is redirected back to the home page in the bottom of the page is a error message:
Fatal error: Call to a member function Execute() on a non-object in /home/stackcup/public_html/shop/includes/functions/sessions.php on line 61
this happened with new customer and existing customers,

I opened the session.php around line 61 says:

59. $qid = "select count(*) as total
60. from " . TABLE_SESSIONS . "
61. where sesskey = '" . zen_db_input($key) . "'";
I have not changed anything on the site, however the server was down and my hosting provider has restored an backup of the site.
what has to go into this file?