Hay, i got it: I used the tip from another reply, that gave me the clue to solve it out:
My problem was actually because the ZA was blocking my anti-virus, not thunderbird itself.
(my antivirus is free AVG, that works together with mail client!)
1-delete the thunderbird instance from the program list of the ZA programs tab
2-delete all instances of your antivirus as well.
Because now you are going to force ZA to re-learn that those programs may have access to the internet.
ZA will ask you, and then you are going to allow it.
Thats it !
Henrique Harveys JF BRA