In VMware’s latest release of vSphere 5.5, vSphere Replication 5.5 was actually released before vCenter 5.5. There is a big issue if you are running vSphere Replication 5.1 and you have Automatic Check and Install Updates selected.
This causes your vSphere 5.1 Replication to automatically upgrade to 5.5 and break your existing replication, meaning you will have to re-install.
This only appears to be the case if you have not already upgraded your vCenter server to 5.5
VMware vSphere Blog: http://blogs.vmware.com/vsphere/2013/09/do-not-install-vr-5-5-yet.html