ConcurrentModificationException when building maven2 multiproject

ConcurrentModificationException occurs sometimes. I counted 3 in about 15 hours, when running a 55 module project.

Stacktrace :
INFO | jvm 1 | 2006/04/19 03:00:03 | Apr 19, 2006 3:00:02 AM org.quartz.core.JobRunShell run
INFO | jvm 1 | 2006/04/19 03:00:03 | SEVERE: Job DEFAULT.DEFAULT_SCHEDULE threw an unhandled Exception:
INFO | jvm 1 | 2006/04/19 03:00:03 | java.util.ConcurrentModificationException
INFO | jvm 1 | 2006/04/19 03:00:03 | at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:617)
INFO | jvm 1 | 2006/04/19 03:00:03 | at java.util.LinkedList$ListItr.next(LinkedList.java:552)
INFO | jvm 1 | 2006/04/19 03:00:03 | at java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1010)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.apache.maven.continuum.buildqueue.evaluator.BuildProjectTaskViabilityEvaluator.evaluate(BuildProjectTaskViabilityEvaluator.java:62)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.codehaus.plexus.taskqueue.DefaultTaskQueue.put(DefaultTaskQueue.java:153)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.apache.maven.continuum.DefaultContinuum.buildProject(DefaultContinuum.java:543)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.apache.maven.continuum.DefaultContinuum.buildProjects(DefaultContinuum.java:436)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.apache.maven.continuum.scheduler.ContinuumBuildJob.execute(ContinuumBuildJob.java:65)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.quartz.core.JobRunShell.run(JobRunShell.java:191)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:516)
INFO | jvm 1 | 2006/04/19 03:00:03 | Apr 19, 2006 3:00:02 AM org.quartz.core.ErrorLogger schedulerError
INFO | jvm 1 | 2006/04/19 03:00:03 | SEVERE: Job (DEFAULT.DEFAULT_SCHEDULE threw an exception.
INFO | jvm 1 | 2006/04/19 03:00:03 | org.quartz.SchedulerException: Job threw an unhandled exception. [See nested exception: java.util.ConcurrentModificationException]
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.quartz.core.JobRunShell.run(JobRunShell.java:202)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:516)
INFO | jvm 1 | 2006/04/19 03:00:03 | * Nested Exception (Underlying Cause) ---------------
INFO | jvm 1 | 2006/04/19 03:00:03 | java.util.ConcurrentModificationException
INFO | jvm 1 | 2006/04/19 03:00:03 | at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:617)
INFO | jvm 1 | 2006/04/19 03:00:03 | at java.util.LinkedList$ListItr.next(LinkedList.java:552)
INFO | jvm 1 | 2006/04/19 03:00:03 | at java.util.Collections$UnmodifiableCollection$1.next(Collections.java:1010)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.apache.maven.continuum.buildqueue.evaluator.BuildProjectTaskViabilityEvaluator.evaluate(BuildProjectTaskViabilityEvaluator.java:62)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.codehaus.plexus.taskqueue.DefaultTaskQueue.put(DefaultTaskQueue.java:153)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.apache.maven.continuum.DefaultContinuum.buildProject(DefaultContinuum.java:543)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.apache.maven.continuum.DefaultContinuum.buildProjects(DefaultContinuum.java:436)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.apache.maven.continuum.scheduler.ContinuumBuildJob.execute(ContinuumBuildJob.java:65)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.quartz.core.JobRunShell.run(JobRunShell.java:191)
INFO | jvm 1 | 2006/04/19 03:00:03 | at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:516)