From: Mark Koennecke <Mark.Koennecke@psi.ch>
I had a jnlp file which did not define the href attribute in the top jnlp tag. This caused openjnlp to die with an undefined reference. Took me quite some time to figure that one out. JavaWebStart runs this file without a problem. And the information required (the source URL) is a parameter to JNLPParser: parseDescription where this problem occurs.