We have a Windows 7 Pro laptop that can't see any of the 300 or so Windows XP and Windows Server 2003 Machines.
It can, however, see all (around 13) Windows Server 2008 and Windows 7 Machines that are on the network. Using \\ServerName\Share doesn't connect, and they don't show up on the network map.
It can ping the servers though. They ping by hostname and by ip address. Other Windows 7 Pro Laptops don't have this same problem!
They are all joined to the domain; servers, laptaps, etc.