Issue with non-core vocabularies

I am using the write-up on the IBM website (http://www.ibm.com/developerworks/library/wa-datasets/) as a guide (thanks for creating that - it has been quite enlightening for understanding the process) and have performed all relevant steps for enabling the DBpedia references. I have simplified the goal, though, to just outputting values from DBpedia in a table from the SPARQL View. I created the SPARQL Views resource type per the article (using label of agency) and added several fields, mapping each field to an RDF data type. I can then display values from DBpedia using these fields in a SPARQL View, per your write-up, as long as I use core RDF vocabularies for the RDF Mapping of the variables (e.g., foaf, rdfs). However, when I try to use non-core vocabularies - for example, RDF Mappings to values in the DBpedia namespace - then I no longer get any data back. For example, if I use an RDF Mapping to dbp:abbreviation (corresponding to http://dbpedia.org/property/abbreviation) and try to display that from the FIELDS in the SPARQL View, then I no longer get any output. (Note that I have tried both dbpedia - as per the article in Table 2 - and dbp as the prefix, but using either of them causes no data to be returned from the DBpedia SPARQL query). I have tried using the 7.x-3.0-beta3 version of Views as well as the most recent dev version from May 13. Is anyone else having such an issue?