I'm not sure what happened, but the delete button no longer erases selected objects.  Also, if I select objects and try erasing them using the erase button on the toolbar, the objects are unselected and the command line asks me to select objects to delete.
 
It seems like AutoCAD is not recognizing when I've already selected an object.
 

Change variable [VAR]PICKFIRST[/VAR], I thing.

That did it.  Thanks!