No internet access again - oh joy.

Hello guys!

I've got Problems with Windows 7 since I bought it - mainly with Internet connection. I'm using Windows 7 Professional via BootCamp on a Macbook Pro, with drivers, of course.
My Firewall is completely deactivated.

It worked fine for a few months, but now my old problem came back:
I try to connect with WLAN (it's a private network, I added it to this... home...network...thingy, don't know what it's called in English, you know what I mean), it takes ages to connect, network is being identified, network can't be identified (you know, this stuff with the bench).
And then, oh joy, "no internet access". I'm tired of seeing that yellow triangle all the time.
Most of the time i get access for a split second after a few minutes, but then it will re-identify the network and, suprise surprise, i don't have access anymore.
Then, when i finally get access and try playing Assassin's Creed Revelations Multiplayer, my NAT is "strict" - that is not possible!
When the problems weren't there for a few months, most of the time my NAT was open within the first five tries. I mean, it was still luck after all.

Sadly, I don't have the slightest clue what could cause this problem. It can hardly be my router, for it works perfectly on Mac.

I tried writing to the Ubisoft support, without success. I also thought I might try contacting the Microsoft-Support, but for some reason (oh JOY) it doesn't recognize my PID and I'd have to pay 70€ for it. Of course I bought the official license.

Maybe you can help me? Otherwise I might end up smashing my Macbook to pieces xD

Lena

(Sorry for my English, I hope you can understand it and I didn't write anything weird- ha!)