>>The Copy button doesn't work in FireFox 3.0 in Downloads and FAQ.
>
>Does it work for you in messages?
>
>For me it doesn't work for regular messages either.

For me it didn't work since FF 0.9 or so, when there used to be something to adjust in about:config, that I can't find anymore, which would allow scripts to manipulate the clipboard. Probably unsafe to start with, which is why it isn't easily enabled in FF.