It sounds like an include file isin't in the correct place. It may be too low, or it may not exist.
Do the paypal server behaviors on the page show as broken? They would if the include reference wasn't on the page at all and you could probably open them and reapply them to fix the problem.
If they aren't broken in the server behavior window you may have to find the include reference:
require_once("../WA_eCart/Adv_CO_Scripts/PP_DirectPayment_PHP.php");
and move it up on the page above the line with the error.
Did this help? Tips are appreciated...
