inexplicable exceptions in Spark 0.7.3

[Walrus theCat]

Hi,

I'm getting this stack trace, using Spark 0.7.3.  No references to anything
in my code, never experienced anything like this before.  Any ideas what is
going on?

java.lang.ClassCastException: spark.SparkContext$$anonfun$9 cannot be cast
to scala.Function2
    at spark.scheduler.ResultTask$.deserializeInfo(ResultTask.scala:43)
    at spark.scheduler.ResultTask.readExternal(ResultTask.scala:106)
    at
java.io.ObjectInputStream.readExternalData(ObjectInputStream.java:1837)
    at
java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1796)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
    at spark.JavaDeserializationStream.readObject(JavaSerializer.scala:23)
    at spark.JavaSerializerInstance.deserialize(JavaSerializer.scala:45)
    at spark.executor.Executor$TaskRunner.run(Executor.scala:96)
    at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)