Ports?

Yet another post in which I'm not sure if I've posted it in the right section. Sorry if it's in the wrong section -.-;;;

Anyway, I can't open ports with my router.

My Router: Netgear - WGR614 v7

I know it's possible to open ports with this router, because it has a special section in the settings to do it in.

I've followed the instructions on the help page, but it never seems to work.

I want to open the ports to be able to host in Warcraft 3: The Frozen Throne.

I've made sure that the port settings in the game match the port settings that I'm trying to play with on the router.

As said though, the ports never seem to stay open.

Sometimes I can host games, but a few hours later, I can't host anymore.

What's up with that?

Thanks for any help