I know that this issue has been brought up before. I've searched these forums, Google and every other source that I can think of and I just can't find a solution. Here's the rundown:

Compaq Presario F700 Win Vista SP1 (fresh reinstall)
Linksys 310N Wireless-N Gigabit router (AT&T DSL connection)

I've tried the basics: disabled firewall, regedit, updated drivers, ipconfig /renew. Nothing works. This is a new system for my client (my in-laws, actually), so this isn't a case of "it just stopped working".

Here's the kicker...

This system connects just fine to my Belkin Wireless-N router and my laptop (also running Vista SP1) connects to their router without an issue.

What am I missing, here? I'm guessing it's an issue of a non-Vista compatible router, but I really don't want to have to buy them another router (they didn't have one before). I need your help.Unidentified Network--Local Access Only... revisited

From what I've gathered, on rare occasions there can be a compatibility problem between a NIC and a router. There was a thread here in the network forum where somebody brought this up.

Just to make sure the NIC is indeed compatible with the router, try booting up Puppy Linux Live CD and connecting to the problematic router. If it works then you've ruled out that possible (rare) compatibility issue. Plugging in a USB wireless adapter could shed some light on the issue, too.

I doubt it's a Vista thing. How about a router firmware update ?

Is the router handling DNS? Or some other appliance. From your description it sounds like the router is handling DNS, but want to make sure.
What are the IP/DNS settings coming up as for the working system. Is it a private IP (192.168.x.x)?.

What happens when you manually configure DNS.
Options:
OpenDNS: 208.67.222, 208.67.220.220
Google: 8.8.8.8