Started a Kubernetes 1.0.1 cluster using VirtualBox 4.3.30. Everything started correctly as:

Validate output:
NAME                 STATUS    MESSAGE              ERROR
controller-manager   Healthy   ok                   nil
scheduler            Healthy   ok                   nil
etcd-0               Healthy   {"health": "true"}   nil
Cluster validation succeeded
Done, listing cluster services:

Kubernetes master is running at https://10.245.1.2
KubeDNS is running at https://10.245.1.2/api/v1/proxy/namespaces/kube-system/services/kube-dns
KubeUI is running at https://10.245.1.2/api/v1/proxy/namespaces/kube-system/services/kube-ui

Accessing KubeUI at https://10.245.1.2/api/v1/proxy/namespaces/kube-system/services/kube-ui prompts for username/password and entered vagrant/vagrant. But the browser keeps waiting for a response and does not show any response.

This was reported at https://github.com/kubernetes/kubernetes/issues/12692 and also at https://github.com/kubernetes/kubernetes/issues/11119.