I suppose the existence of two simultaneous languages is making the difference in my computer :'(
Well, everything's possible, but I doubt it... I have as many languages installed as possible and didn't encounter any related problems.
Igor and Vlk, thanks for debbugging my problem.
I uninstalled, installed version 4.1.357, updated it to 4.1.418, two languages (English and Portuguese).
No troubles... Let's walk forward
(Btw, Vlk, your avast4.mdb file did not solve the problem)