Shopping cart not updating

Hi fellow zen cart'ers

Im new to these forums so i wasnt sure where to ask this question but i thought i would try here.

Just recently my website has had an issue where by a customer selects a product and clicks "add to cart" but it doesnt get added to the cart.

this is the error which also came up;; Fatal error: Call to a member function Execute() on a non-object in
/home/th/the/thebikeshedmortdale.com.au/public/www/includes/functions/sessions.php
on line 72

the site is www.thebikeshedmortdale.com.au

Any help on how to resolve the issue would be GREATLY appreciated!!!!!

Ok so i fixxed that in the code using an old thread i found, but i still have one error message in the admin control on zen cart,

Warning: file_exists() [function.file-exists]: open_basedir restriction in effect. File(/home/customers/thebip/includes/languages/english/bikeshed/other_images_names.php) is not within the allowed path(s) in /home/th/the/thebikeshedmortdale.com.au/public/www/admin/includes/functions/general.php on line 2849

The site seems to be working, though i wouldnt mind sorting out this error message....

The 2 paths referenced do not appear the be even close to the same.
You might check your 2 configure.php files for anomalies as to paths.

This is an older version and I don't recall the issues with a version past the last 2 or so.