Vista only works with pre-Windows 2000 AD Logon name?

Why can't I get any Vista (even Business and Enterprise) version to accept a
FQDN user logon into an AD file share? It only works with pre-Windows 2000
user logon name. If the client is on the domain I can log into the
workstation with FQDN and then access file shares the logged in user has
rights too. However if a share is accessed from a Vista client not attached
to the domain I am forced to use the pre-Windows 2000 logon name. XP clients
not attached to the domain did not have this limitation, FQDN names work with
XP.

Thanks for the attention to this question in advance.