I don't know why it doesn't work for you...
I use FF2 and it works with that version.
I have turned off autostart to use it only when I'm shopping and doing bank business.
It's process isn't running, but it still works...

In FF2 anyway...
I haven't noticed any bugs with FF2...
I have had to restarted it once since it came out.
If you upgrade your browser, i think that you have to install v-engine again.
Hopefully someone else will be able to help you some more.