This is entirely a PayPal issue. PayPal is the one you should be contacting because they are delaying the sending of their IPN. This is NOT a Nanacast issue. You should take this up with PayPal support and find out why their system is delaying sending the IPN.
I explain the entire issue, what it is, how it works, and why it happens and what you can do about it here:
http://nanacast.com/docs/paypal
While I do suggest you hound PayPal about it and demand that they fix their IPN I doubt you will get anywhere with them. They have bad support when it comes to their systematic weaknesses because they are such a huge company. This has been an issue for years. Just do a good search on Google for "PayPal IPN delay" and you will see.
Additional keywords: pending status, redirect, delayed IPN