Although there has not been any official acknowledgment from PayPal, they seem to be having another spate of occasional missing/delayed IPNs within the past day or so, according to a pattern of support requests we've noticed and this thread on PayPal's Developer Forum:
http://www.paypaldeveloper.com/pdn/board/message?board.id=ipn&thread.id=14351
As you know, our system relies on receiving PayPal's IPNs to log a transaction, notify you of a sale, grant the buyer access to a thank-you/download page and issue the buyer a thank-you email with download link.
Since the nature and extent of the issue is unknown at present -- some-to-most IPNs appear to be coming through okay, but it is unknown if any missing IPNs would eventually get issued later or if they simply got dropped -- we would recommend using your Seller Admin > "Send free thank-you email/download link/codes" to satisfy customers who have paid (which you can verify manually in your PayPal account) but have not received their link or codes yet.
