Hi jamesl,
Can you share with us how much memory your VM originally has/had? Did you increase it and try again?
I'm thinking that if the VM only runs Kibana and X-Pack it would probably need at least 2G to get past that optimization step.
For testing purposes I usually install the full stack on one VM and give it 6GB. But that's with Elasticsearch, Kibana, Logstash, and a couple of Beats running.
Lee