Sergey,

>You've to set (about:config)

signed.applets.codebase_principal_support true

That's the one! ;-)

>> Seems to be some delay in this happening for some reason.
>
>I think delay is intentational so people would read a message before clicking Allow button.

As good a reason as any...

>>IAC, anytime I now use the function I get the prompt, and for the convenience it is worth it and should allay any security concerns you might have. Note also that the link you pointed to says this was 'fixed' in the preview release. I am still running the preview release. Works for me?
>
>I just tested in 1.0 and it works the way you describe it.

Good to know. Thanks for the bailout!