Hi Paul,
Not sure if you tried this already but:
Also - want to get your attention to the below in the Release notes:
• Utilities: • OpenSM: InfiniBand Subnet Manager is provided as a sample code. The sample code is intended to allow users to test or bring-up the InfiniBand fabric without a management console / switch (to get started). For cluster production environments, Mellanox's recommendation is to use a Managed Switch or the UFM-SDN Appliance.