Hey Niaz,
Just an FYI, I was having a problem with the Simple Facebook Connect plugin. I've disabled it and all of my problems are now fixed. I have no idea what Simple Facebook Connect is doing, but for whatever reason it was jerkin' around my shopping cart.
Here's the error message I was getting when I clicked proceed to checkout:
Fatal error: Call to a member function checkCartInventory() on a non-object in /home/george/public_html/wp-content/plugins/wp_shopcart/models/WpShopcart.php on line 665
Here's the relevant code that's breaking:
public function checkInventoryOnCheckout() {
if($_SERVER['REQUEST_METHOD'] == 'GET') {
global $post;
$checkoutPage = get_page_by_path('store/checkout');
if( isset( $post->ID ) && $post->ID == $checkoutPage->ID) {
$inventoryMessage = WpShopcartSession::get('WpShopcartCart')->checkCartInventory();
if(!empty($inventoryMessage)) { WpShopcartSession::set('WpShopcartInventoryWarning', $inventoryMessage); }
}
}
}
This is the line that's breaking:
$checkoutPage = get_page_by_path('store/checkout');
After disabling Simple Facebook Connect, everything works fine.
If anyone else out there wants to have their blog post to their Facebook Wall or Twitter, I'd recommend using a service called dlvr.it