Interesting discussion around this retraction.  The results were not fraudulent nor were the observations wrong, but the conclusions had to be refined based on a limitation in the reagent.  Should such a thing be retracted?  I don't think so.  If we had to retract everything that was wrong, we'd have a slim scientific literature indeed.  Should it be flagged and annotated?  Absolutely!  More reason why reagents need careful identification and linking.  See a related discussion on Retraction Watch:  http://retractionwatch.wordpress.com/2012/06/27/should-linus-paulings-erroneous-1953-model-of-dna-be-retracted/