turn off your firewall & check your antivirus doesn't watch/block internet traffic.
If it doesn't help, then it's either an issue with your router (then manually setting the port forwarding should help), or some issues at your ISP level.
If you can, check with another PC to be sure it's not related to your Windows, drivers or hardware.
== Mana Games ==
>> I don't answer Private Message, except if it's really a _Private_ topic <<