I run into the same issue, and even after re-install of DHW i receive this error related to the Plugins
Check if the plugin is available in the plugins subdirectory of the Kettle distribution
/opt/kaltura/dwh/logs/log_events_events.log:2016/06/30 16:14:20 - file_processing_job - ERROR (version 4.2.1-stable, build 15952 from 2011-10-25 15.27.10 by buildguy) : Unable to load class for step/plugin with id [ConcurrentSafeCombinationLookup]. Check if the plugin is available in the plugins subdirectory of the Kettle distribution.
/opt/kaltura/dwh/logs/log_events_events.log:2016/06/30 16:14:20 - file_processing_job - ERROR (version 4.2.1-stable, build 15952 from 2011-10-25 15.27.10 by buildguy) :
/opt/kaltura/dwh/logs/log_events_events.log:2016/06/30 16:14:20 - file_processing_job - ERROR (version 4.2.1-stable, build 15952 from 2011-10-25 15.27.10 by buildguy) : at org.pentaho.di.trans.step.StepMeta.(StepMeta.java:239)
/opt/kaltura/dwh/logs/log_events_events.log:2016/06/30 16:14:20 - file_processing_job - ERROR (version 4.2.1-stable, build 15952 from 2011-10-25 15.27.10 by buildguy) : ... 10 more
root@video:~#
Any idea?