Make sure that you have the appropriate firewall exceptions made in Windows Firewall, and any other 3rd party firewall applications you have running on your machine. I'm not sure what ZA does in particular, but these are the important firewall exceptions that need to be made in Windows.
On XP:
Make sure that "UPnP Framework" has a firewall exception.
On Vista:
Make sure that "Network Discovery" and "Windows Portable Devices" both have a firewall exception.
You may want to view your ZA logs to see what it is blocking when you attempt to wireless sync. Note what it is blocking, then see if you can make an exception for it.
Let us know how it goes...
Thanks!
Matt Akers
Zune Product Team
.: This posting is provided "as-is" with no warranties, and confers no rights :.