I am now aware of issues with the ComboBox column and System.RunTime type.
However I do not exclude the possibility for a bug present in the ComboBoxColumn logic for member access.
It would be very helpful if you could provide some code illustrating how you create and bind your business objects to the grid and to the cobmbobox column .
In case we find any bug in the RadGridView a fix will be provided for the very next internal build.
the Telerik team