Display network posts on root site with Network theme

We are trying to create a site that has at it's root (mfc.ammatconsulting.com) a page of updates from all the sub-networks. To do this I have set the setting to "Network Posts". However, this seems to work on the sub-sites (where I don't want it) (i.e. mfc.ammatconsulting.com/williamsdb) but not on the root site where I do! I am throughly confused. Also the box that allows you to exclude sites to show on the network posts is pre-populated with no way of changing the content.