Rancher 1.2 and nginx-proxy failing

After upgrading to Rancher 1.2 - actually re-installing - none of my nginx-proxy and letsencrypt-companion stuff is working any more for containers managed by rancher.

It looks like nginx-proxy is not picking up when containers are started - and therefore not generating the configs needed to route traffic to the containers.

Has anyone else seen this problem?

This is a major issue - as it is the only way I can easily have an easy to use proxy with built in service discovery and letsencrypt certificate generation.