With no changes on our side and perhaps related to POODLE/SSL3 our PayPal API call to PPIPNMessage::validate is now failing with.
SSL routines:SSL3_READ_BYTE
I second that. Lost hours trying to figure it out. On my IPN listener I had to remove 'force ssl v3'. From that moment on my IPN start working again.
Just do a curl -v https://paypal.com
It shows: SSL connection using TLS_RSA_WITH_AES_256_CBC_SHA