I'm not sure why that works; it shouldn't, but it does.
That's why I call it a workaround instead of a fix.
Once you have an interesting looking Prog Id, do a Google search to find more about it.
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.
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.
On two of the Macs, as soon as I fired up the Citrix app, the Java vpn window would show 'error'. Then I remembered that I had done some Java development in the past and installed various jdks from Oracle so I ran: That was on the working Mac.
The applet is a simple vpn client from Juniper that lets me access a Citrix Desktop from any Mac that I can install the Citrix receiver client on so I can work on 'Company stuff' from a large screen i Mac when I'm sat at home or from my Mac Book when I'm on the road (it works fine over 3/4G).
The first thing is that you have to do some configuring of both Java and Safari to get the applet to run at all.
I'd be curious to know from Mac OSXHints users whether they are experiencing this problem in the first place and if the workaround works for you, too.
What was happening on the not-working Macs was that the jdk versions were being used, and the Juniper vpn client won't work with them.
To fix things for the moment I simply removed the jdk folders.
Then I remembered the difference between 'System' Java, Java plugins, and Java development kits.
Simply put, you can have multiple versions of Java in different places.