Yeah that's a tough one. Seems every "cart" action causes the blank page. Deleting from cart, changing amounts, adding, etc. I stand by syntax error, but now believe its higher up in the workflow hierarchy. Looking at my carts as though my cart was doing that, I came up to main_cart_actions.php and wonder if that's where the problem is. Since none of the main cart actions work, I'd be combing that page for the errors, (missing semi-colon, curly brace). Also, I didn't create an account so if the errors you speak of behave differently for those logged in I didn't check that. I tried some paypal stuff on your site too and would also suggest checking includes/application_top.php for syntax. In fact, probably more so than the cart_actions. Print out some variables along the way and see what is empty or missing.