I'm not exactly sure how or why, but could it be to do with DLS, DistributedRowMatrix, TimesSquaredJob etc still using mapred.JobConf instead of mapreduce.Job?
I ask because when I give DLS a sequence file that's been created from the latest ToItemPrefsMapper and ToUserVectorReducer I get the exception. However when I use versions that still use mapred I don't get the exception.
