eh...it does seem that when I tried that....my ip address seem to have changed! and when I tried to go to the site using my ip address...the website couldn't be brought up!
I would say you arent using a static IP address... so every time you restart your computer your IP address has the possibility of changing (depending on network usage).
http://portforward.com/networking/static-xp.htm Is how to set up a Static rather than Dynamic IP address.
DMZplus mode is (what I would assume) a De-Militarized Zone setting of some kind which is inbuilt into your router... Just looking up my image to explain DMZs:

Unless your network is set up like that I wouldnt recommend having that setting enabled...
One final thing... Sometimes with routers (like mine) to save a port forward, you must "Save" and then immediately restart your router with the "save and restart" function or something similar.
I hope I can help if you have any further problems.