Unable to convert System.String to CustomObject

[Tommaso Caldarola]

I have a custom collection of custom objects.

I bind a DataGrid with collection1, a property of custom object is a
ReferenceType (another custom object).

For that property in the datagrid I see a combobx, when the user selects an item
I get the following error:

Unable to update data. Unable to convert System.String to CustomObject type.