Kafka producer error

I keep seeing these errors in my code that is just trying to send some data
using an AsyncProducer:

kafka.common.FailedToSendMessageException: Failed to send messages after 3
tries.

at kafka.producer.async.DefaultEventHandler.handle(Unknown Source)
~[kafka_2.10-0.8.0.jar:0.8.0]

at kafka.producer.async.ProducerSendThread.tryToHandle(Unknown Source)
[kafka_2.10-0.8.0.jar:0.8.0]

at
kafka.producer.async.ProducerSendThread$$anonfun$processEvents$3.apply(Unknown
Source) [kafka_2.10-0.8.0.jar:0.8.0]

at
kafka.producer.async.ProducerSendThread$$anonfun$processEvents$3.apply(Unknown
Source) [kafka_2.10-0.8.0.jar:0.8.0]

at scala.collection.immutable.Stream.foreach(Stream.scala:547)
[scala-library-2.10.1.jar:na]

at kafka.producer.async.ProducerSendThread.processEvents(Unknown Source)
[kafka_2.10-0.8.0.jar:0.8.0]

at kafka.producer.async.ProducerSendThread.run(Unknown Source)
[kafka_2.10-0.8.0.jar:0.8.0]

2014-10-30T01:40:45.176Z ERROR [ProducerSendThread- ]
[k.producer.async.DefaultEventHandler] {}: Failed to collate messages by
topic, partition due to: null

2014-10-30T01:40:45.506Z ERROR [ProducerSendThread- ]
[k.producer.async.DefaultEventHandler] {}: Failed to collate messages by
topic, partition due to: null

2014-10-30T01:40:45.647Z ERROR [ProducerSendThread- ]
[k.producer.async.DefaultEventHandler] {}: Failed to collate messages by
topic, partition due to: null

2014-10-30T01:40:45.772Z ERROR [ProducerSendThread- ]
[k.producer.async.DefaultEventHandler] {}: Failed to collate messages by
topic, partition due to: null

2014-10-30T01:40:45.890Z ERROR [ProducerSendThread- ]
[k.producer.async.DefaultEventHandler] {}: Failed to send requests for
topics myTopic with correlation ids in [169,176]

2014-10-30T01:40:45.892Z ERROR [ProducerSendThread- ]
[k.producer.async.ProducerSendThread ] {}: Error in handling batch of 29
events

I created the topic before starting using bin/kafka-topics.sh. I checked
zookeeper and seems like the topic was indeed created. Any ideas?