This problem could be somewhat related to this bug filed against Java Web start in Java SE 6 update 7:
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6725426
The GlassFish Java Web Start feature makes use of a similar sort of method on the Java Web Start class loader, to locate a downloaded JAR file. In update 7 Java Web Start is no longer returning the expected JarFile instance, as it was in update 6. I need to investigate some more to see exactly where the change is.
- Tim
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