An extended property on an XML index on '{0}.{1}' has corrupt metadata, and cannot be associated with the XML index. The ...

An extended property on an XML index on '{0}.{1}' has corrupt metadata, and cannot be associated with the XML index.  The extended property will be omitted from the model.  This can happen when databases are upgraded from SQL Server 2005 to SQL Server 2008.  Recreating the extended property in the database should fix the problem.