Unable to save Pro Sites settings page

HI,

I have a fresh install of WP with multisite enabled and configured. I disabled all the plugins and then installed your wpmudev-updates plugin. Then I used that to install Pro Sites plugin. All seems to be working OK except the Pro Sites settings page. When I click to save the page it takes a long time then takes me to a browser error page that says page can not be loaded connection was reset.

I have uninstalled and re-installed everything several time but still have the same problem.