Here try this , it will reset your TCP/IP stack and the Winsock ..
TCP/IP stack repair options for use with Windows XP with SP2.
For these commands, Start, Run, CMD to open a command prompt.
Reset WINSOCK entries to installation defaults: netsh winsock reset catalog
Reset TCP/IP stack to installation defaults. netsh int ip reset reset.log
Press enter after each command , hopefully this might do the trick . Also , try removing your wireless adapter from Device manager and reboot the system , Vista will reload the drivers .