@LostInIgnorance:
I had a problem like this a bunch of times. If you end up changing the IP of the interface where the captive portal is running on, it tends to think it is still using the old IP. I never did figure out what caused it, but even after reboot or disabling and re-enabling the captive portal, the IP wouldn't change. I know there is a place through shell to edit the address manually, but I never did find it. Easiest thing that I had found being a newbie, just start from scratch, setup all the IPs, then enable the captive portal again.
Thank you for your answer. I also think if i do a factory defaults reset it will work then but it's a bit tough for me to do that now.
If somebody knows how to edit the address of the captive portal manually from the shell please share :)
I found a some config files but are not the right ones for editing manually the portal ip : lighty-CaptivePortal.conf and lighty-webConfigurator.conf