Hello, I`ve tried to fix this problem by myself during 3 days, and now im totally out of ideas...

The problem is that many people can`t connect to my server, but meanwhile, some of my mates can do it. And it`s really strange.
Let me clear more for you about my situation: Windows 7 x64, TS3 Server x64, TS3 Client x64, Static IP (78.36.6.158), required ports are forwarded (UDP 9987, TCP 10011 and 30033), ISP said that they are not blocking anything for me.
And ofc, some of my mates can connect me, furthermore, sites like http://gametracker.com/ can see and scan my server too. But I rly have no any ideas why some ppl can connect, and some - not.... Can someone help me with it?
Sorry for some mistakes, english is not my native language.