Try getting a serverlist from my ftp-server:

ftp://whitedragon.dyndns.org/gnutella.net

copy it into your LimeWire folder overwriting your old gnutella.net.

This should help you getting connect. Most ISPs don't block port 6346, - instead they simply block the public pong caches which you need to connect.

I'm updating my serverlist several times a week, so you shouldn't have any problems connecting with it.

By the way, LimeWire updates this gnutella.net file, once it is connected, automatically, so you won't need this file every time you want to connect to the network.