New Post: Using PropertyGrid with EnumDescConverter

As a workaround, you can replace the line

if( markupProperty != null )

with

if( ( markupProperty != null ) && ( markupProperty.PropertyType != typeof( object ) ) && !markupProperty.PropertyType.IsEnum )

in DescriptorPropertyDefinitionBase.UpdateAdvanceOptionsForItem().

Looks like the call to "markupProperty.Value" is not working for enums or objects.