Vista - Laptop with Vista can't connect to wireless router?

Before I moved to my new apartment, my set-up was as follows: Cable modem ->
Vonage device (built in router) - > Wireless router -> PC and laptop.
Everything worked fine. After I moved I changed it to: Cable modem ->
Wireless router -> Vonage device (built in router), PC and laptop. Vonage
device and laptop were not able to get online so I had to switch back to my
old set up. Everything works fine except my laptop.

The error message that I get when I click on "Diagnose problem" is that
either the DNS server is down (cannot ping www.microsoft.com) or that it
pinged the DNS server but no response. I'll get a "no response" error message
when the DNS server is set to 192.168.15.1 which is the IP scheme for the
Vonage device. I have DHCP set-up but I still manually changed the DNS server
to 192.168.0.1 (wireless router scheme) and thats when I get the "DNS server
is down error".

Why would the DNS be set to 192.168.15.1 when the IP and gateway are
192.168.0.xxx and 192.168.0.1?

I already reset both the Vonage device and wireless router (reconfigured
both, had to be on the phone with Vonage to get the Vonage device
reconfigured), ipconfig /flushdns, disabled IPv6, checked hosts file, nothing
works.

What can I do? Whats going on? Thanks!!

PS. Laptop can't connect to internet even if I plug in an ethernet cable and
it CAN connect to the internet just fine using my neighbor's wireless network.