Checkboxes in a datagridview not holding value

I have a datagridview who's datasource I populate with a generic list.  This generic list ("buyers" - plural) is a collection of lots of custom class objects ("buyer" objects).  All of the properties belonging to a buyer object display as columns in the datagridview (when connected to the grid's datasource)...so far so good.  Consider that one of the buyer object's properties is a boolean that I just now added to the code.  When the datagridview displays all of its data, this boolean property is expressed as a column of checkboxes -- which is just what I want.  The problem is this: when I click on any of those checkboxes, no mark shows.  Note, that that particular column is not readonly, so the core cause must be something else.  Ideas?

BTW, the generic list "buyers" inherits from "system.componentmodel.bindinglist"; not sure if this has any bearing on the problem.