See thread in the Ubuntu Forums:
Ubuntu is really pushing OpenJDK, and Sun / Oracle Java no longer appears in the default repository. So if someone were to install Java from a default Ubuntu 10.04 install, the only option they have is OpenJDK unless they figure out how to add repositories.
When running PC Gen on OpenJDK on Ubuntu 10.04, the skills and feats tabs go completely blank on the SRD 3.5 player source (may occur on other sources, but didn't test).
As with the other users in the Ubuntu forum above, the solution was to completely uninstall OpenJDK, add the Lucid repositories, then install Sun Java. All of the problems I was having with OpenJDK do not occur when SunJava is installed.