Having installed Windows Vista (x64 and x86), I had some "weird" interactions with my Snap Server 1100.
I believe I have it resolved after changing a security policy option:
Local Security Policy\Local Policies\Security Options\Network Security:LAN Manager authentication level
Send LM & NTLM - use NTLMv2 session security if negotiated
(Default: Send NTLMv2 response only)