Thanks for your support. It is a correct answer.
I just did the point 3 (thanks to another user) and it run the same, withouth running sap as administrator. In fact, as you can read in my question, everything run on my system, and I have the problem only on a pc, but ping is ok, and everything else, too.
Anyway, I think your solution is deeper and runs well, so I check it as "correct answer".
Regards
Daniele