@amonteronstruo
You're using the OpenJDK (Which is the Ubuntu default). You need to install the 'official' Sun JDK. Try installing package 'sun-java6-bin' and you should be fine. When you run 'java -version' after installing that package you should get:
java version "1.6.0_15"
Java(TM) SE Runtime Environment (build 1.6.0_15-b03)
Java HotSpot(TM) Server VM...