I had the same problem on my new 15" MBP when running Win 7. My solution was:
1. Click the small network icon in the lower right corner
2. Click "open networks and sharing"
3. Click "manage wireless networks"
4. Right-click on your network and select "properties" from the context-menu
5. Check the "connect even if the network are not broadcasting SSID" box
At least that worked for me.
PS. I have a norwegian version of win 7, so it's only a rough translation.
Tom