@cyberfox - kaspersky is great but it can be tricky to "disable"; I use it on some machines and am having no probs running sbox, just saying, if you want to start eliminating variables that's one to look at.
The other place to look is your firewall, router, and whatever else is in place locally before you get to your ISP. You responded "tried, still doesn't work" in response to a suggestion that you look at your firewall and disable your AV and whitelist sbox in your AV. Did you actually turn off the firewall temporarily to see if it was the culprit?