Oh, that is good news. I hope that the solution sticks.
The "IPN Message Reattempt" is exactly what it sounds like. It tells PayPal to reattempt delivery of IPN messages. It is supposed to function as a fail safe, in the event the UPN message is not received successfully by the website. It is not supposed to spam a site like it did in your case. Perhaps, PayPal has introduced a new glitch.
In any event, I noticed during testing that the IPN messages rarely failed to be sent. The ratio was perhaps 1 in every 1,000 - 2,000 messages. And keep in mind during testing we were slamming the PayPal sandbox pretty hard with purchase orders. Sometime ordering 10 - 15 subscriptions every 10 - 20 seconds. So, I think you're pretty safe turning that feature off.
~ All the best