Ok, I think I'm able to narrow down what is causing the issue. It's not the act of opening, but it is the act of drawing or adding anything to a map. I can create a new map with no basemap (empty drawing) and everything works fine. As soon as I add anything to it (create empty feature class, ESRI basemap, shapefile), then the program goes into an endless cycle of processing (most options are greyed out in the menu). Not sure if that helps narrow down what the issue is at all.
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