Hello seeksam,
Please feel free to contact me if you are still experiencing issues with this scenario.
In order to detect value changes in a Bound/Unbound checkbox column, theCellValueChangedclientside event of the edint core may be used, as described at:
http://ko.infragistics.com/community/forums/t/68619.aspx
Hope this helps. Please feel free to contact me with any questions.