If your ComboBox column does not display values until you edit one of the values, check to make sure you populated the DataSource of the ComboBox before populating the DataSource of the Grid.
// BAD |
gridBindingSource.DataSource = _Repository.GetGridData(); |
comboBindingSource.DataSource = _Repository.GetComboData(); |
// GOOD |
comboBindingSource.DataSource = _Repository.GetComboData(); |
gridBindingSource.DataSource = _Repository.GetGridData(); |