I have a client, behind a firewall, that invokes an applet which uses the
Sun extension javax.activation in Sun's activation.jar (JavaBeans Activation
Framework Specification). My Applet is digitally signed, and installs no
problem. Additionally, the manifest for the jar for the applet specifies
correctly the extension requirement for the activation.jar, and where to
download it from:

Manifest-Version: 1.0
Created-By: 1.4.0 (Sun Microsystems Inc.)
Class-Path: GGUser.jar Extension-List: activation
activation-Extension-Name: javax.activation
activation-Implementation-URL: http://ggrip.com/activation.jar

My problem is that this client, behind a firewall, gets a
sun.misc.ExtensionInstallationException when his system attempts to install
activation.jar from the above manifest in my applet. The activation.jar is
digitally signed by Sun.

I do not know what is causing this -- it may be, I think, a problem caused
by his firewall (on other systems, it seems to install ok)? Any ideas would
be greatly appreciated. Below is the stack trace from the client's computer
which in installing the applet, pops the exception on the activation jar.
Also enclosed, below that, is the manifest from activation.jar. Thank you,
Ike

sun.misc.ExtensionInstallationException: User denied installation of
http://ggrip.com/activation.jar
at sun.plugin.extension.ExtensionInstallationImpl$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.plugin.extension.ExtensionInstallationImpl.installExtension(Unknown
Source)
at sun.misc.ExtensionDependency.installExtension(Unknown Source)
at sun.misc.ExtensionDependency.checkExtension(Unknown Source)
at sun.misc.ExtensionDependency.checkExtensions(Unknown Source)
at sun.misc.ExtensionDependency.checkExtensionsDependencies(Unknown Source)
at sun.misc.URLClassPath$JarLoader.parseExtensionsDependencies(Unknown
Source)
at sun.misc.URLClassPath$JarLoader.getClassPath(Unknown Source)
at sun.misc.URLClassPath.getLoader(Unknown Source)
at sun.misc.URLClassPath.getResource(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at sun.applet.AppletClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadCode(Unknown Source)
at sun.applet.AppletPanel.createApplet(Unknown Source)
at sun.plugin.AppletViewer.createApplet(Unknown Source)
at sun.applet.AppletPanel.runLoader(Unknown Source)
at sun.applet.AppletPanel.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Here is the maifest of Sun's Activation.jar if this helps:
Manifest-Version: 1.0
Implementation-Version: 1.0.2
Specification-Title: JavaBeans(TM) Activation Framework Specification
Specification-Version: 1.0
Extension-Name: javax.activation
Created-By: 1.3.0 (Sun Microsystems Inc.)
Implementation-Vendor-Id: com.sun
Implementation-Vendor: Sun Microsystems, Inc.
Specification-Vendor: Sun Microsystems, Inc.
SCCS-ID: @(#)jaf.mf 1.1 02/03/15

Name: javax/activation/MimeTypeParseException.class
SHA1-Digest: uxV3qLHRu5JTOFrHnJXm13AO+0M=

Name: javax/activation/CommandInfo.class
SHA1-Digest: 1cKS/VKDQRQtAdvjQSJXZfjuKnM=

Name: com/sun/activation/viewers/ImageViewer.class
SHA1-Digest: gEg0GCvDjyJ0wogJ+Yqs5pkgMe8=

Name: javax/activation/MimeTypeParameterList.class
SHA1-Digest: bCozM0t+J3YcJVez99Mw8jo4ES0=

Name: javax/activation/DataContentHandlerFactory.class
SHA1-Digest: 7sK1N48hT5JuGK4CPHqlDB648/8=

Name: javax/activation/DataSourceDataContentHandler.class
SHA1-Digest: YioWWrfLNtVjS7sPDORm1VCljO8=

Name: javax/activation/DataSource.class
SHA1-Digest: esP7C47kvDVsS/yoBAst31EiDhM=

Name: com/sun/activation/registries/MimeTypeFile.class
SHA1-Digest: o3xR9NwzCphDNomc9i79cx/4rUo=

Name: com/sun/activation/viewers/TextViewer.class
SHA1-Digest: SDcybqXjPt6lB7MFTekaMQLo1XU=

Name: com/sun/activation/viewers/TextEditor.class
SHA1-Digest: v/CQ9F0afPiGfz3Q5QYgDH8KGVY=

Name: com/sun/activation/registries/LineTokenizer.class
SHA1-Digest: 5S1ZtvDD0IoSHNKT8gZed6wXdVw=

Name: javax/activation/DataContentHandler.class
SHA1-Digest: 4ScrMQQptqNulV+va+UAbeyWgCY=

Name: javax/activation/MimeType.class
SHA1-Digest: JdIXzJFjK4hSwodWVaxE2CpK4Lk=

Name: javax/activation/FileDataSource.class
SHA1-Digest: NinT1KJWqpl6RFJGz0QKyWTXxrc=

Name: javax/activation/SecuritySupport.class
SHA1-Digest: AyfISvmRrTO6f4dj59Snyelc6Ck=

Name: javax/activation/MailcapCommandMap.class
SHA1-Digest: eYZxYHjNOLV8L2zhfHapZWuFuuo=

Name: javax/activation/DataHandler$1.class
SHA1-Digest: YgB/hf89aSawmFGr0mlwtjccfeI=

Name: javax/activation/SecuritySupport12$1.class
SHA1-Digest: LM3BWLOz1fNRnw2w8LxwA/Kijr4=

Name: javax/activation/DataHandler.class
SHA1-Digest: 9ueMkf2LOQO706JazRAeOZ+L2Eo=

Name: javax/activation/SecuritySupport12$3.class
SHA1-Digest: t17MgFzefsEODCAhdr0Sp9wz5/Q=

Name: javax/activation/SecuritySupport12$5.class
SHA1-Digest: 9mZfG3X19Jtaf5ycmmfSMeknnkk=

Name: javax/activation/SecuritySupport12$2.class
SHA1-Digest: 7gljiWPdXVdl4MFwa7Y0QYy9sxM=

Name: javax/activation/SecuritySupport12$4.class
SHA1-Digest: DLnWjma9u5+oqsMUEs6p3WN+ReQ=

Name: com/sun/activation/registries/MimeTypeEntry.class
SHA1-Digest: RjQc1npYLzmhAl8Tcm70Ge0QeqA=

Name: javax/activation/SecuritySupport12.class
SHA1-Digest: f51IilsGhzv/KqVP3eEGPT8KLLA=

Name: javax/activation/MimetypesFileTypeMap.class
SHA1-Digest: SBVy1zEsibhu302G2b8lgbNfg2k=

Name: javax/activation/FileTypeMap.class
SHA1-Digest: hD5elx7xhmbFWb68dgDXeMsz0A0=

Name: javax/activation/CommandObject.class
SHA1-Digest: qvYPNnH4j2UUfQ0BnRPxamLezf4=

Name: javax/activation/DataHandlerDataSource.class
SHA1-Digest: RdeKh/ecCa0+yJw3SYDaEfwXCo8=

Name: com/sun/activation/registries/MailcapTokenizer.class
SHA1-Digest: zSjxxhDskZteW4bJMALwI/gtMdU=

Name: javax/activation/ActivationDataFlavor.class
SHA1-Digest: 2GgoZECWpZ79tTYE8AZYgzwMSTY=

Name: com/sun/activation/registries/MailcapFile.class
SHA1-Digest: 7Ynl9y+DzEy1icHtnpCU/l5RuIc=

Name: com/sun/activation/registries/MailcapParseException.class
SHA1-Digest: je7BwM327P5pb4asLCB74OOm6h0=

Name: javax/activation/ObjectDataContentHandler.class
SHA1-Digest: MvBEMcpyrIFvj0WWesKTQ1Xof/Y=

Name: javax/activation/URLDataSource.class
SHA1-Digest: /aYv/WOFrGRrW3CjsleMIIVgedY=

Name: javax/activation/UnsupportedDataTypeException.class
SHA1-Digest: G1LVjur46DQFrps5HysTEqRM/NA=

Name: javax/activation/CommandMap.class
SHA1-Digest: shlnOhsM3rvKxwBNt5bBy6Z550c=

Name: com/sun/activation/viewers/ImageViewerCanvas.class
SHA1-Digest: hYOFlCZpdmIyCgfulKuL+9YuYM0=