In Vista, IE runs in a special protected mode. When running plugin applets in IE, when we try to store resources into the default cache directory in the user's home, it will get redirected to another folder under the user's temporary internet files. So later if the user wants to view the cached resources via java control panel, the cache viewer will show nothing in the cache because the cached resources are not store in the default location.
This also prevents the sharing of cached resources between webstart and plugin.
Applet still runs fine in IE7.
We need to investigate and see where should we move the default cache directory when running vista.