I'm working on a signed Applet that will no longer start under version 7u21 of the JRE, and I've been able to isolate the problem to the Java Plugin's cache. If I disable Temporary files in the Java Control Panel, then everything's file. If I enable Temporary files, I get this exception in the Java console on startup:
basic: exception: com.sun.deploy.net.DownloadEngine$2 cannot be cast to com.sun.deploy.cache.CacheEntry.
ExitException[ 3]java.lang.ClassCastException: com.sun.deploy.net.DownloadEngine$2 cannot be cast to com.sun.deploy.cache.CacheEntry
at sun.plugin2.applet.JNLP2Manager.loadJarFiles(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
The applet is being deployed using Oracle's deployJava script.
This is happening on all our test systems in Chrome, FireFox, IE 8 and 9, which reinforces that this is a plugin problem. It's currently impacting a production system that's been running just fine for over a year before this JRE update.
Any insight anyone has would be greatly appreciated.