simple extension doesn't work

This bug exists so I don't forget about this problem.

Customer says attached JNLP app doesn't work properly, customer email follows:

here is a jar file with all the necessary components for problem number 2:
- MyFrame.jar is the jar file with the main class MyFrame that is going to
be executed. It is located in the subdirectory "ui".
- MyLabel.jar is the jar file with an additional class MyLabel (an
extension) that is referenced by MyFrame. It is located in the subdirectory
"extensions".
- myframe_orig.jnlp is the JNLP file which works. It takes both jar files
from the same directory, no extensions specified.
- myframe.jnlp is the JNLP file that does not work. It specifies an
extension MyLabel which points to a JNLP file mylabel.jnlp.
- mylabel.jnlp. References the jar file MyLabel.jar. It is located in the
subdirectory "extensions".

The application just displays a Frame with a label in it.