Some news:
I've update my system from Catalyst v10.4 to Catalyst 10.12 (Video+Chipset) and realtek v2.48 to v2.56 and problem solved !!!
My wife system is a little old and there are no new drivers for it, so I'm using the latest legacy drivers: Catalyst v10.2, Nforce 15.53 and realtek v2.47 and i Still getting the problem. The only driver i can update is the audio driver, but i doubt that it is the culprit, because in my system only with the video+chipset update the problem was solved.
Wrong conclusion !!! The culprit is Comodo Firewall v4.1. Updating Comodo to v5.3, avast 5.1.889 works flawless. In my XP netbook, both (comodo v4.1+Avastv5.3) works without problems. Probably something with 64bits platform.
