PayPal IPN Warning from Plugin?

Hi!
I have had this issue for weeks. I called PayPal and they said it is plugin related.
Can you see which one?

Thanks

Here is the mail from Paypal;

Please check your server that handles PayPal Instant Payment Notifications (IPN). IPNs sent to the following URL(s) are failing:

http://jonsavagegallery.com/order-received

If you do not recognize this URL, you may be using a service provider that is using IPN on your behalf. Please contact your service provider with the above information. If this problem continues, IPNs may be disabled for your account.