Thanks for this post. It seems Esri still hasn't fixed this bug. Using ArcMap 10.2.1, with a file geodatbase, I got repeated crashes using the Mulitpart to SinglePart geoprocessing tool as well as trying to explode multipart features. However, converting to a shapefile, both the geoprocessing tool and exploding features in an edit session work just fine.
The bug (NIM079950) we found with Rob's data was fixed in Aug. 2011 and went in 10.0 SP5. The problem was very data specific. I have just retested the case using our current development version, it worked fine.
For those who have seen issues in 10.1 or 10.2.1, please email me (email@example.com) your test data, as fewer features as possible that still can reproduce the issue. It is likely a different problem.