In AccurevSCM.java, the method getStreams(...) can return null (and sometimes does, as the AccuRev client executable sometimes fails to work).
In method pollChanges(...), getStreams is called, the result assigned to a Map and then the map is interrogated without a null check.
This can (and does, sometimes) throw a NPE (and the logging, aside from showing where the faulty code was, gives no clue as to what the plugin was trying to do, what accurev command failed and what error(s) it reported).