http://support.microsoft.com/kb/928233/en-us

Windows Vista cannot obtain an IP Address from certain routers or from certain non-Microsoft DHCP servers

Consider the following scenario:

  • You connect a Windows Vista-based computer to a network.
  • A router or other device that is configured as a Dynamic Host Configuration Protocol (DHCP) server is configured on the network.
  • The router or the other device does not support the DHCP BROADCAST flag.

In this scenario, Windows Vista cannot obtain an IP address.