When Nexus prepares the list of repositories (in Repositories Maintenance or Repositories Configuration screens) one gets the "Loading" animation for more than 30 seconds, then it disappears but the list of repositories remains empty. Some more investigation shows, that nexus tries to reach the configured proxy repositories with an HTTP HEAD request. For some unrelated reason it takes 15 sec until each request is answered. Seems there is a timeout in Nexus somewhere that cuts off the process before it can finish. In that case it would be better to display the configured repositories even if they cannot be reached in time. Otherwise, it is impossible to change the configuration via the web interface. Btw. the same seems to happen on the groups configuration screen when a group is selected. The list of available repositories just remains empty.