I was able to find a solution to my problem.
Let me restate my problem.
I have a java application which uses POI XSSF to read and write excel 2007 workbooks to the users 'My Documents' folder.
The application functions as designed when run through eclipse, dos batch file launch or directly (double clicking on the app jar file).
It does not work correctly when launched through jnlp. The final stack trace shows it is a security issue: unable to write temporary file
The jnlp is initiated from my pc. This runs the app jar file which is located on a secured network directory.
or jnlp --> main jar
Note: I have security set to all-permissions in the jnlp.
The solution was to create another java app which, by using dos commands, launches the desired app jar.
So I have jnlp --> intermediate jar --> main jar
Mike