I’m having a similar problem, in that orders and payment are being received by Paypal, and I am getting the money and the new order notification email.
However, after Paypal has finished processing the order it redirects to my site, but the page is totally black (as in nothing but white in the browser). The URL reads:
…/galleries/gallery-name/receipt
Is there a ‘receipt’ page missing that I need to set up?
Furthermore, no email is getting through to the buyer, even though I am getting a purchase notification and the money is entering Paypal.
Finally, the sale is not registering in the admin section of the site.
Following the above advice, I have configured Paypal so the IPN URL is my homepage and that message delivery is enabled.