User jasuha1 on the java.net forums has reported a problem with the scoping of JSObjects. The attached test case loads the same web page three times in separate iframes. Each applet instance fetches the JSObject associated with the surrounding window. One of the iframes is then destroyed. The JSObjects associated with the other applet instances have then been invalidated.
This is a regression compared to the old Java Plug-In.
There is clearly a problem in the distributed reference counting scheme used by the shared LiveConnect code.
Links to associated forum threads:
The attached test case also crashes the Firefox 3 port of the new Java Plug-In if it is the first applet launched in the browser session. This must also be investigated.