I would guess that you need to be looking at opening the ports related to azureus >>>>
So, what are NAT problems?
NAT is Network Address Translation, which means that there is something between your PC and the internet making the connection. This device can be either a firewall or a router, and it needs to be properly configured for Azureus to run.
§ For a firewall, you need to open the ports used by Azureus in TCP. By default from 126.96.36.199 on, it is only port 6881.
§ For a router, you need to forward the ports used by Azureus in TCP. By default from 188.8.131.52 on, it is only port 6881.
So to solve that kind of problem, please refer to your manual to set up your device correctly.
Taken from click here
Port forwarding info click here