When I attempt to Add a Basemap (e.g. OpenStreetMap, Bing Maps Aerial, etc.) to an empty map in ArcMap 10 it consistently crashes. I'm using ArcMap 10.0 build 2800. Based on what I read in the forums, I turned off the Hardware Acceleration (Customize > ArcMap Options > Data View tab). It still crashes.
When I try to Add Data from one of ESRI's GIS servers (at server.arcgisonline.com) I can see the various data sources/map services (e.g. USA_Topo_Maps). But when I try to Add it, I first get a Warning message, "Warning, inconsistent extent" (I don't have a map file open at this point). If I click on the OK button, it adds the basemap layer to my map.
So it appears to be in the "Add Basemap" functionality.
FWIW, a month ago I was able to Add a Basemap without a hitch.