If you no longer have access to the old email address (if you do, you can just re-add it and accept the payment), the customer can cancel the payment, but you might want to call PayPal and explain the situation as they can sometimes forward the payment to your account - it saves having to get the customer to cancel and pay again after generating an invoice from PayPal.

For future reference, updating email addresses in eBay and PayPal doesn't update the address on old listing templates etc, as when you list an item it always pre-fills the last address you used when listing, even if you start a new listing from scratch.