<groupId>org.apache.avro</groupId>
<artifactId>avro-mapred</artifactId>
<version>1.7.4</version>
<classifier>hadoop2</classifier>
the hadoop2 version is for cdh4. I think the fix is simply removing "hadoop2" from the project/build.scala file on the cdh3 branch:
Seq(
"org.apache.avro" % "avro-mapred" % "1.7.4",
"org.apache.avro" % "avro" % "1.7.4",
"com.thoughtworks.xstream" % "xstream" % "1.4.4" intransitive(),
"com.googlecode.kiama" %% "kiama" % "1.5.0-SNAPSHOT",