When a standalone ESX 5 host is added to vRanger's inventory, and that Host is "associated" with a vSphere 5 vCenter not in vRanger's inventory, replication operations to that host will fail with the error
"<host> is being managed by a Virtual Center. Please disassociate the host from the Virtual Center before continuing a replication operation or register the Virtual Center in vRanger"
"Association" is a new relationship introduced in vSphere 5, whereby some host resources are managed only by an associated vCenter, and not the host itself. The Host, therefore, does not have permission to perform the operations required to replicate a VM. If the vCenter is not in vRanger's inventory, vRanger cannot obtain the required permissions.
Either disassociate (not just disconnect) the host from the Virtual Center, or register the Virtual Center in vRanger.