L2J Server

Now I'm not sure where problem is, but most likely not with server, since my login does not even see their attempt to login. However I've installed proper L2 client and patched with system I know works fine (clean one with GG killer + hosts file). Yet a soon as he tries to connect to my server, gets disconnect. And 5 of his friends too, according to him.

Did anyone encountered similar problems anytime?

My thoughts is that his ISP might be blocking something, but other servers works fine, so...

Please give me any ideas where to look for a problem.

DNS, Firewall, ISP

firewall is configured to let it through, his isp is silknet. no idea where that's from. no idea if they are blocking something and why would they... dns... do you mean address itself by it?

most likely they are playing from a net cafe, usually when there you tend to copy the system over the old one, tell them to delete the system folder and apply yours again.