Help needed with Netgear wgr614v6

[teulk]

Ok ive just got myself the above and im pretty stumped with the port forwarding. Prior to this i had a Peak router and forwarding the ports was a doddle and worked flawlessly. The problem im having is ports that im forwarding are disappearing and i have to keep adding them. Single port ranges are fine i.e 7695-7695, however multiple port ranges keep dropping off the list ie 36578-36588 and i dont know why. Can anyone help. The purpose of forwarding the ports is to allow me to host a game and as of yet no one can join my server. The ports are correct as they are what i used in my previous router and that worked fine. I have a static IP also