The first thing is that you have to do some configuring of both Java and Safari to get the applet to run at all.
Once that was all done, I could log in from all my Macs, fire up the applet and establish a secure connection. I made sure that the Safari and Java preferences were set the same on each machine but still no joy.
Web applets still use the up to date, secure version 1.7 plugin.
[crarko adds: I believe Oracle has said that eventually Java will no longer support applets at all, on any platform.] A few weeks ago, a number of people started reporting having trouble with Siri.
We respect its storied history, and value the contributions of its many readers, but we can no longer support it at the level it deserves.