When we were using Oracle Jinitiator to access Oracle E-Business suite application, I couldn’t get it to work in Linux. I tried several suggestions, but nothing worked. We finally moved to Sun Java JRE from Jinitiator. That helped a lot in getting it to work. I was getting this error message when we were using Jinitiator. I still see the message with Java, but it works.

  In order to access this application, you must install the J2SE Plugin version 1.6.0_XX on your client and NPX_PLUGIN_PATH environment variable is set before starting Netscape. To install this plugin, click here to download the oaj2se.exe executable. Once the download is complete, double-click the oaj2se.exe file to install the plugin. You will be prompted to restart your browser when the installation is complete.

To get Java to work, use Synaptic package manager or whatever manager you use for installing programs in Linux. Search for sun java 6 and select sun-java6-jre (or whatever the latest version) and also select sun-java6-plugin. Install them. Once installed, Open a terminal from Application – Accessories – Terminal, type
directory (if you are using a different version of Firefox than the default one, then the directory name might be different) and press enter. Then type
and press enter (don’t forget the period at the end) where XX is the current Java version. At the time of this post, I think Java 1.6.0.15 is the latest.
Restart Firefox and try starting the Oracle E-Business suite application.