Index: sites/all/modules/ecommerce/cart/cart.module
===================================================================
--- sites/all/modules/ecommerce/cart/cart.module	(original)
+++ sites/all/modules/ecommerce/cart/cart.module	(modified)
@@ -126,9 +126,9 @@
   switch ($op) {
     case 'login':
        // Convert their cart session to a permanent user cart at login.
-      if (isset($_SESSION['cart_id'])) {
-        db_query("UPDATE {ec_cart} SET cookie_id = %d WHERE cookie_id = '%s'", $user->uid, $_SESSION['cart_id']);
-        unset($_SESSION['cart_id']);
+      if (isset($_COOKIE['cart_id'])) {
+        db_query("UPDATE {ec_cart} SET cookie_id = %d WHERE cookie_id = '%s'", $user->uid, $_COOKIE['cart_id']);
+        setcookie('cart_id', null);
       }
       break;
   }
@@ -943,6 +943,7 @@
   }
   elseif ($sid = session_id()) {
     // Use session id until the user registers, then switch to user id.
+	setcookie('cart_id', $sid);
     return $sid;
   }
 }
@@ -1029,7 +1030,7 @@
   // Rebuild the items hash
   $items = cart_get_items(NULL, 'rebuild');
   if (empty($items)) {
-    unset($_SESSION['cart_id']);
+  	setcookie('cart_id', null);
   }
   if (!strstr(request_uri(), 'cart/view')) {
     drupal_set_message(t('Your item(s) have been updated.'));
@@ -1072,7 +1073,7 @@
   }
 
   $cookie_id = ($cookie_id) ? $cookie_id : cart_get_id();
-  unset($_SESSION['cart_id']);
+  setcookie('cart_id', null);
   return db_query("DELETE FROM {ec_cart} WHERE cookie_id = '%s'", $cookie_id);
 }