If you guys are facing problem with Vista wifi connectivity then here are some of the most common fixes that can help you. I had collected some very useful links from Microsoft website that offers fixes for a number of wifi problems in Vista. I am sure that can help you out to deal with the problem you are facing.
1). This link help you to understand the issue behind IP address. Sometime the system fails to collect a proper IP from the DHCP due to which you get the problem.
Windows Vista cannot obtain an IP address from certain routers or from certain non-Microsoft DHCP servers
2). The second link is based on the performance problem after connectivity. You can find out some quick tips to improve the wifi performance on Vista.
You may experience connectivity issues or performance issues when you connect a mobile PC that is running Windows Vista or Windows 7 to a wireless access point
3). This link is based on authentication issue. I had seen some threads on this website where people has complained about fail authentication on the network.
How to enable computer-only authentication for an 802.1X-based network in Windows Vista, in Windows Server 2008, and in Windows XP Service Pack 3
4). This another helpful link to deal with issue behind DHCP on subnet.
DHCP Does Not Obtain a New Address When EAP Reauthenticates Across Access Points with IP Subnets That Differ
5). Problem occur when your system fails to collect a proper IP config when DHCP is not active.
When a DHCP server is unavailable on a Windows Vista-based computer, Windows Vista uses an APIPA IP address much sooner than Windows XP does under the same circumstances
6). Problem related to Vista connectivity with off-link addresses.
Windows Vista cannot connect to any off-link addresses when the default gateway is configured to be the same as the client IP address