I don't understand why one form of traffic would work, yet others (ping, telnet) would not.

Can you ping other servers? Can you telnet anything else? It might be worth testing other servers. If this doesn't work, your traffic is being blocked.

Do you use a VPN or other kind of proxy? Who is your ISP? Is your router set to forward any ports or block any traffic?

If the ISP is blocking the website specifically, then it would work via a proxy. If it's your PC, then if you have a phone - download a telnet app and try connecting from your wifi. Then use the same settings in a cafe or something to see if the same settings work elsewhere.

What OS are you using? Is your firewall blocking anything?

Any of the above might help narrow down the problem and where it is in the pipe.

Yhorian