=== modified file 'uc_product_kit/uc_product_kit.module'
--- uc_product_kit/uc_product_kit.module	2009-01-23 14:41:22 +0000
+++ uc_product_kit/uc_product_kit.module	2009-01-26 18:24:48 +0000
@@ -510,12 +510,13 @@
         $node->content['products'][$product->nid]['#weight'] = $product->ordering;
       }
     }
-
-    $node->content['add_to_cart'] = array('#value' => theme('uc_product_kit_add_to_cart', $node),
-      '#weight' => 10,
-    );
+    if (module_exists('uc_cart')) {
+      $node->content['add_to_cart'] = array('#value' => theme('uc_product_kit_add_to_cart', $node),
+        '#weight' => 10,
+      );
+    }
   }
-  elseif (variable_get('uc_product_add_to_cart_teaser', TRUE)) {
+  elseif (module_exists('uc_cart') && variable_get('uc_product_add_to_cart_teaser', TRUE)) {
     $node->content['add_to_cart'] = array('#value' => theme('uc_product_kit_add_to_cart', $node),
       '#weight' => 10,
     );