This helped me when I couldn't access any of my Vista (ultimate) machines from any other machine (Vista as well as XP)
In the Security Policies console lies the answer
1) Open 'Run' from the start menu and type "MMC.exe secpol.msc" (without quotes) and hit enter.
2) MMC will open with the Security Policies console.
3) Click the arrow (expand) 'Local Policies' and click on 'Security Options'
4) Look to the right pane and look at the 3rd entry: "Accounts: Limit local account use of blank passwords to console logon only" and set tat to diabled.
5) that should allow anonymous File Sharing Access from other locally networked computers.
I couldn't access any of my folder shares even though they were staring me in the face. Everytime I accessed one I got the same error you received. Basicly, when you share a folder using File Sharing, it opens the folder to 'Guest' access. by default Guests need no password. So when you use on PC to access another PC's shared folders/files it uses blank passwords for simplicity, but Vista (at least in Ultimate) enabled a blank password policy that limits their use to the locally administered console only.
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