I can't connect with Windows XP help!

So whenever I try and connect to my wireless router, the connection process hangs up at ''reading network address'' (or something like that, I have the french version of XP). After some time, the connection reads ''limited or non-existing connection'' (again, french version). The problem being that the DHCP server does not allocate a lan address to my computer.

However, if I boot on my mac partition (it's a Macbook pro with BootCamp) my internet is fine. So this rules out a problem from my isp, my network is functional and my wireless card is functioning properly.

I tried restarting my router and modem many times, with no success. I gave a bigger pool of addresses that the DHCP can allocate (from 8 to 100) with no difference. My connection worked fine before, and I never changed my drivers so I doubt it's that, and the card itself like I said before is not broken because it works on OS X.

I also ran Avira anti-virus and Spy-Bot, in case maybe it was a virus that was doing all this. DId not change anything.

What is strange though, is when I try and manually give an address to my computer, with the router IP and DNSes, the connection says it's established. I'm ''connected'' to my wireless network. However, the connection does not give nor receive any packets. I can't even connect to the router by typing the router's IP in firefox.

I'm all out of solution D:... any help?