FULL PRODUCT VERSION :
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) Client VM (build 14.0-b16, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 5.2.3790]

I confirm I'm using Windows XP x64 Edition, but I reproduced the problem with JRE 1.6.0_u14 32-bit version, starting the Java Web Start 32-bit client on a JNLP downloaded with a 32-bit browser (Firefox 2).

Anyway, I just checked that the same problem occurs even if I use the Java Web Start client of the 64-bit 1.6.0_u14 JRE release.

A DESCRIPTION OF THE PROBLEM :
When you try to launch an application through JNLP and the JNLP files requests an eager download of a JAR which does not contain anything (just META-INF with the signing information), Java Web Start fails and the application is not started.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Please see steps to repro of bug #6533653

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The application should start. The empty JAR is signed and should not give any problem to the Java Web Start client.

This DID work with Java 6_u13, 6_u12, 6_u10, 6_u5...
ACTUAL -
The application is not started and an error dialog is shown by the Java Web Start Client.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
In the Java console I read:
#### Java Web Start Error:
#### Un'applicazione non firmata ha richiesto l'accesso illimitato al sistema
Risorsa non firmata: http://sun2.ost.lan:8080/cardinis-ost/applet/conf.jar
(translated: an unsigned application has requested unlimited access to the system. Unsigned resource: http://sun2.ost.lan:8080/cardinis-ost/applet/conf.jar)

Please note that conf.jar is actually signed!

In the details of the error dialog shown by Java Web Start client I read:

JNLPException[category: Errore di protezione : Exception: null : LaunchDesc:
<jnlp spec="1.5+" codebase="http://&lt;server&gt;:8080/path/to/codebase" version="1.0">
  <information>
    <title>App Name</title>
    <vendor>Vendor Name</vendor>
    <homepage href="Vendor home page"/>
    <description kind="short">App Description</description>
    <icon href="http://&lt;server&gt;:8080/path/to/icon.gif" kind="default"/>
  </information>
  <security>
    <all-permissions/>
  </security>
  <update check="always" policy="always"/>
  <resources>
    <java href="http://java.sun.com/products/autodl/j2se" version="1.6.0_14"/>
    <!-- CUT other JARs defined -->
    <jar href="http://&lt;server&gt;:8080/cardinis-ost/applet/conf.jar" download="eager" main="false"/>
    <property name="swing.defaultlaf" value="javax.swing.plaf.metal.MetalLookAndFeel"/>
    <!-- CUT other JARs defined -->
  </resources>
  <applet-desc name="App Name" main-class="com.package.AppletMainClass" width="400" height="200">
    <!-- CUT params definition -->
  </applet-desc>
</jnlp> ]
at com.sun.javaws.LaunchDownload.checkSignedResourcesHelper(Unknown Source)
at com.sun.javaws.LaunchDownload.checkSignedResources(Unknown Source)
at com.sun.javaws.Launcher.prepareLaunchFile(Unknown Source)
at com.sun.javaws.Launcher.prepareToLaunch(Unknown Source)
at com.sun.javaws.Launcher.prepareToLaunch(Unknown Source)
at com.sun.javaws.Launcher.launch(Unknown Source)
at com.sun.javaws.Main.launchApp(Unknown Source)
at com.sun.javaws.Main.continueInSecureThread(Unknown Source)
at com.sun.javaws.Main$1.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Remove the empty JAR from the JAR list declared in the JNLP file.

Release Regression From : 6u13
The above release value was the last known release where this
bug was not reproducible. Since then there has been a regression.