There are issues with null values not correctly binding without using a custom binder.

See demo project here: http://www.kendoui.com/code-library/mvc/grid/binding-nullable-field-to-dropdownlist-editor-in-grid.aspx

Forum post here: http://www.kendoui.com/forums/mvc/grid/nullable-property-in-grid-doesn't-update-(when-bound-to-combobox).aspx