A day or two ago, Apple silently forced TLS only on gateway.sandbox.push.apple.com, which is used by developers to test push notification systems. The production system has not changed (yet). I suspect this was a reaction to the heart bleed bug. While they have said that none of their services were impacted it seems curious that this would happen at the same time.
If you are experiencing push issues on the sandbox (particularly disconnects), make sure you are using TLS. You can verify that your push certs are working ok with APNS pusher ( https://github.com/blommegard/APNS-Pusher ).
Push sharp users should update.