PHP session problems

Hello everyone. I am working on developing a webstore for a friend of mine. http://www.houseofslack.net/dysfunction2 and I am having this peculiar problem. When I get to my cart.php file through posting a form (for example, when you click on an item, and click add to cart), it rememembers my session variable $olist and cart.php displays all the items in that array. here''s the weird thing though, if I just hyperlink cart.php from a page, it keeps the same session id and everything, but there is nothing in $olist. it seems to clear it out. I checked my code on cart.php and there''s no session_destroy() or resetting of the $olist variable. so I''m wondering if this is a common problem because it just doesn''t make any sense to me. anyone else run into this problem and fix it?