I had the same problem until this morning. Acquiring network address because the router wasn't assigning an IP to my XP machine. It couldn't see it, though I saw the network connection. I don't know if this will help you or not, but here's what I did to finally fix the problem. I logged into the router (192.168.0.1). Clicked on Setup, then Wireless, then "Manual Wireless Network Setup". I changed the 802.11 mode to "802.11g only" and viola! I waited a few minutes and everything was connected perfectly and my laptop now had an IP address. My XP machine doesn't have 802.11n and mixed mode wasn't working. I knew both machines had 802.11g, so I selected that option only.
Anyway, I wrestled with this darn setup for 3 days, so I know how frustrating it is. My solution may very well not work for you, but I thought I'd at least mention what I did to resolve a similar problem.