For the last few days I've been trying to configure my network so I can play some game online. In order to be able to do that it seems I need to open some ports: 2300-2400, 4001 and some other 40.xxx.

My network looks like this: Thomson SpeedTouch 516v6 modem, ADSL with PPPoE + a Linksys WR54G wireless router. My PCs are connected to the router and share the Internet connection. Internet works fine.

I have configured the modem to open the specified ports (in relation to the router). I have also configured the router to open up the specified ports. Problem is, the ports do not seem to be open!!! 4001 and 40k seem to always be closed. Ports 2300-2350 seem to be open, while 2350-2400 are closed (should be 2300-2400 range).

Yes, I do have the latest firmware for the router. I also have some other port open for some other program. Works fine. Most of the time... Also tried DMZ. More open ports, but still not all of them. No firewall (software, Windows default, router or modem).

What could be causing this?

Just opening the ports does not forward them to you. You need to go in the routing table on the router and forward the ports a static IP assigned to your PC.

Also, isn't that Thmoson SpeedTouch also a router + modem? If that's the case, then you need to go into that as well as the linksys router and open all the ports there as well.