HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

The infamous c comp has been completely removed. There is no router. I have NOD antivirus, but I played normally with it before.

True, I changed my provider, and I have a dynamic IP. Maybe that's the reason, I don't know.

This doesn't apply to you, but to Opp, to his router:)
And also... Somewhere around half of those claiming that they don't have a firewall actually do have one. And in general, NOD can also be the "source" (this is what NOD sounds like in general, but if you look at the configuration, especially after some update).