I'm trying to construct a network dataset for (almost) the first time. I've assembled a number of feature classes in a geodatabase feature dataset. When I rightclick and select new network dataset and then begin to set the network properties, the option to "select the feature classes that will participate in the network dataset" only shows me a subset of the feature classes in the geodatabase. The others, which are point shapefiles that I want to include in the network, don't appear. Why would this occur, and what can I do to fix it so I can add them to the network?