after installing all the add-ons I used to use on FF 3.0.2, I found that they are installed correctly but do not appear on the program.
add-ons:
Dr web
forecast enhanced
no script
adblock plus
IE View
McAffee site adviser
US Eng Dictionary
Mr Tech Toolkit
Mina, this could happen, indeed it happened to me in the past with older versions.
Sometimes you need to uninstall the extensions, install again.
I were lucky: they’re working from me since I’ve updated from Firefox v.2…
it worked ;D thnx 
I wouldn’t even expect it would be that easy ;D
Hi Minacross and Tech…
What does Mr. Tech Toolkit do? Did Tech design it? ;D
Best Regards…
;D ;D that’s funny…
ardvark, check this link/ please.
Hi Minacross…
Thanks! 
I had no idea it would be a toolbar for music, RSS, etc., I was thinking a system or browser utility or configuration tool of some kind. ;D
Best Regards…
It’s not mine. I’m not a programmer/developer 
It manages the add-ons installations, list them, allows version by-pass, remove the ‘security’ button time for installations, etc.
Hi Tech…
That’s ok, you know a lot about avast and other software.
Best Regards…