Spark on Yarn: Kryo throws ClassNotFoundException for class included in fat jar

[Nicholas R. Peterson]

I'm trying to run a Spark 1.4.1 job on my CDH5.4 cluster, through Yarn.
Serialization is set to use Kryo.

I have a large object which I send to the executors as a Broadcast. The
object seems to serialize just fine. When it attempts to deserialize,
though, Kryo throws a ClassNotFoundException... for a class that I include
in the fat jar that I spark-submit.

What could be causing this classpath issue with Kryo on the executors?
Where should I even start looking to try to diagnose the problem? I
appreciate any help you can provide.

Thank you!

-- Nick