Running Hadoop distribution CDH3U1

I have been able to use HDFS with data-integration thus far and I haven't run into any problems except for a strange logging issue:
I noticed that after restarting the job and task trackers, the nodes are no longer logging properly, i.e. logging to the normal path/log halts altogether.

When I remove the HADOOP_CLASSPATH variable from and restart the trackers, logging resumes normally.

Any ideas whether this is a bug with my specific distribution, or with PDI-BD in general?