solution doesn't generate pfds under Linux

I have a web client solution that generates pdfs and displays them in the browser window. The pdfs are created and placed in a folder, then the web client points to that file and opens it using the Adobe Reader browser plugin. The solution works fine on Windows, but there is a problem when I move the solution to a machine running Ubuntu Linux 8.04.1. The pdfs do not get generated. I click the link in the solution to generate the pdf and display it, but I get error 404. I look in the folder where the pdfs get placed, but it’s empty. My only clue is servoy_log.txt. It has the following lines that occurred when I tried to generate the pdf:

2008-08-18 11:20:54,587 ERROR [http-8080-exec-1] com.servoy.j2db.util.Debug - Throwable
java.lang.IllegalArgumentException: PdfReader not opened with owner password

I don’t know what PdfReader refers to. There is no file or method with that name. I get the error even if I run the solution as root. If it matters, I’m running Ubuntu in Virtualbox 1.6.4.
Can anyone tell me what this error means? I can post the rest of the log file if I need to.

Version 3.5.6-build 519
Java version 1.5.0_15-b04 (Linux)

This error comes from itext library which we use for pdf operations. It means an encrypted pdf is tried to be accessed without owner password. Strange this happens only on windows … You can create a case about this ( with a sample and explanations about how to reproduce it) in our support system, then someone will have a look.