The easiest, dirty way to test for blocked ports.
Go to the telnet prompt,by going start, run and type “telnet+ the I.P. address of the remote gateway, + one space and the port that you are testing”
Like “telnet 216.240.120.120 1720”
If you get a white screen, and under the options, the only posibility is “disconect”, then you are conected to the port, and there is no blockage.
If you time out after + about 30 seconds, and you are sure the port is open at the other end, then the ISP is playing with you.
Best luck!!!!!!!