I have
Server1 Win2008 Storage Server Running DFS Access-based enumeration - off Offline settings - disabled
Workstation1 WinXP SP3 32bit
Workstation2 WinXP SP2 64bit
I have a shared folder on Server1 on the DFS share. Workstation1 can see all files and folders. Workstation2 does not. I have tested with multiple WinXP 64bit PCs and the same files across these machines do not show up. Going directly to the files via the address bar works.
WinXP 64-bit has many problems. Stick with 32-bit or upgrade to Vista or Windows 7 if you want/need 64-bit.
Issue is prevented/avoided by going to the UNC share via ip address.