Can you attach a little sample project showing the problem, or submit a Direct Trac support incident with a sample? That would likely be the quickest way to get things resolved.
You could try creating a second GridListControl celltype and use it exclusiively for this problem column to see if that would make things work.
this.gridDataBoundGrid1.Model.CellModels.Add("SpecialGridListControl", new GridDropDownGridListControlCellModel(this.gridDataBoundGrid1.Model));
this.gridDataBoundGrid1.Binder.InternalColumns[2].StyleInfo.CellType = "SpecialGridListControl";