Refinement Panel - Property doesn't exist

http://www.glynblogs.com/2011/01/create-a-content-type-search-refinement-panel-in-sharepoint-2010.html

1. New Managed Property --> Map
2. "Select Add Managed Property to Custom Set results set retrieved"
3. Full Crawl
4. Refinement Panel on Search --> Add Category with the Mapped Property Name.
<Category    Title=”My Managed Property”   Description=”Allows refinement by My Managed Property” Type=”Microsoft.Office.Server.Search.WebControls.ManagedPropertyFilterGenerator”    MetadataThreshold=”5″    NumberOfFiltersToDisplay=”4″    MaxNumberOfFilters=”20″     ShowMoreLink=”True”    MappedProperty=”MyManagedProperty”    MoreLinkText=”show more”    LessLinkText=”show fewer”    />
Note: Type: This has to be the TaxonomyFilterGenerator for Managed Metadata fields (for other fields you use the ManagedPropertyFilterGenerator class)
5. Search Core Results --> Uncheck the Location Visualization --> Add Column in Fetched Properties
6. Full Crawl and Done.

Note: Managed property there is an property called ‘Retrievable’ that allows whether the property can be used in queries. Turns out that the Content Type managed property is set to false, and try as I might you can’t change that (unless someone knows a way?)
http://www.sharepointanalysthq.com/2011/01/refining-on-content-type-in-sharepoint-2010/