I'm getting this whenever I try to customize any field property in the Mapper.

BusinessLayerException
 An error occurred while refreshing the data from field 'DTEproject_item_exceptionsBO.piex_readonly' to property 'Checked' on control 'chkReadOnly.'  Are you missing FieldPropertyDescriptor for a custom property?
ArgumentException
 Column 'piex_readonly' does not belong to table DTEproject_item_exceptions.

Could you guys give me a clue ?

Thanks.