Most routers wouldn't cause a problem, because most routers don't interfere with outbound connections, only inbound connections (Read up on client and servers). Gamesurge whom I've been with for years and am actually on right now, will only connection refuse in a few incidents, you've been glined (global ban on all servers) and it detects it and just drops you. Second, it will do this if you try to access a bad port. Very seldomly will it drop you due to countermeasures to stop people from reconnecting to an unlinked server possible due to what they have as "(*.net *.split)".
What I suggest is try manually connecting to each of their servers, if they all refuse its most likely a ban. Resources:
http://www.gamesurge.net/servers/ - Server list
http://www.gamesurge.net/utils/gline/ - check for active Glines on your address
http://www.gamesurge.net/chat/ - Java client
http://www.gamesurge.net/ - Main Site
