ComboBox & GetStandardValues always returns string values

Hi,

I have a typeConverter that returns a list of 'MyType' objects in the StandardValuesCollection. However when i select an item in the list box it always returns a string item and not the 'MyType' object itself. I've looked at the messages that are returned from ConvertFrom and ConvertTo and the destination type is always of type system.string.

I've tried using
'<propgrid:PropertyEditor ValueTemplateKey="{x:Static propgrid:BuiltinEditors.DynamicValueTemplateKey}" PropertyType="{x:Type local:MyType}" />'
as well as other ideas but when i select an item the property grid combobox it always returns a string value.

Am i mising something simple here?

Thanks in advance

John K.