You can always ask your ISP to change your IP to static. Normally you can do this this yourself in the router settings or under Network Connections.
However, if you have opened the ports and the problems still occurs then there must be a conflict. These could be mean multiple things:-
-Wrong IP address/computer name in the port forward rule.
-DMZ Zone maybe disabled in the router. DMZ Zone is an open all ports rule. Add your IP Address to the DMZ Zone and enable it.
-Ports being opened by other port forwarding rules. If the ports are being used by other port forwarding rules, you can change GunZ's default ports in the config XML to ports that aren't being used.
-Wrong port type settings. You need to open both ports on TCP and UDP.
-Change the router firewall to minimum security to allow inbound and outbound connections.
-If your router provides it. Change the routers firewall policy to allow "Wan to Lan".
If none of the above work, I suggest scanning the ports using Advanced Port Scanner - http://www.advanced-port-scanner.com/
