I cannot connect to port 3997

I have just moved into a new flat with a new internet service provider (x-net). I use the voice chat program Ventrilo on a daily basis, using the IP 202.60.88.170 and the port 3997. With my new internet service provider I cannot connect to port 3997. I attempted to connect to this channel using my flatmate's computer and it did not work, so i know it is not a problem with my computer. I successfully connected to another server that Ventrilo provides, so i know it is not a problem with the program. I ran a tracer prgram and was sucessfully able to connect to the sever, but when i ran a telnet to attempt to connect to the server and the port, i could not do so. I contacted my ISP and told them of my problem and they say that it is not an issue on their side as they do not block this port. They suggested it is an issue with the modem or router. I do not know how to solve this problem, I am extremely frustrated and at my wit's end. Does anyone know why I cannot connect to this port, and what I need to do to be able to connect to it?