My Network Places cannot display computer name!

Windows 2003 Server
Windows XP Client (50 PC) in the domain

All the client can connect to server. All the client can using my network place to view another computer name of share folder.

But when I using 2003 Server "My network Places". I only can see the server name, all the client name are disappear.

I have try to ping the client computer name, it no problem of connection. When My Network Place cannot display computer name in server only?

Thanks!