Hi Aaron,
Did you customize the Location Field layout by any chance? I see the navigation control is looking very different in your attached snapshot. If you did, can you please verify that it used to work prior the modifications to the Location Field being made (please make sure you backup your customization prior making any tests!)? Also, can you open the LocationOnMapStartupMapDocument.xaml file that is located under ArcGIS Configuration Files document library and verify that the basemap layer has a valid url. Finally, if nothing of the above works, I would suggest installing Fiddler and checking when you open a list item to see what message you will get from the server for that basemap layer. You should be getting some error and can post the saved stack from Fiddler here. This is the first time we hear of this issue, so I am not sure what might be going on there. We verified that on a clean install of ArcGIS for SharePoint 2.1.1 all works as expected.
Regards,
Elitsa Baklova