So it's just that one feature class causing issues; might be something with one or some of the records in that feature class. Can you try loading the data using the method I described above for that one feature class? In ArcCatalog, right click the 10.2.1 feature class and click Load, then pick your source 9.3.1 fature class and map the fields. Usually, if there are issues with specific records, the Simple Data Loader will list the OBJECTIDs so you know what needs to get fixed.