Port Forwarding Snow Leopard

So, let's see if the community can help me out on this
i've done this before (not so many times tbh) and i remember it worked fine, so i'm not sure what i'm doing wrong now:

I wanted to open some ports on my MacbookPro, to play an online game:
I go to my router(Belkin):

Virtual Servers

add the port i would like to see open.

save, and i thought that was it (i had other ports, already enabled)

i've also checked the steps here, after to see if i did something wrong:

PortForward.com - The Default Port Forwarding Guide for the Belkin F5D8633-4

BUT

it doesn't seem to work, if i go here:

Open Port Check Tool - Test Port Forwarding on Your Router
or here:
Open Port Check Tool

but it always says that the port is closed, also network utilities doesn't see the port as open. I've also tried this program Port Map and TCMPortMapper.

I also turned off, both my OS Firewall, and my router firewall, to try, but still the same result.

I'm sure i'm doing some stupid mistake, so please point it out

Or let me know if you need any additional infos. I'm on Snow Leopard

I don't think i've changed nothing relevant, in my internet/mac configuration lately, and i think it worked fine before

eg i was hosting a minecraft server, with the proper port open and it worked fine.

Any idea?

I remembered it as something fairly simple to do, but it's giving me an headache.

Thanks

Really, no idea at all guys??
Please this is getting me crazy!!