Samba problem, can't connect as a different user

[Chris G]

I am trying to connect to several shares on my Fedora 8 system as
different users from a Windows XP system.

I can't get the "Connect using a different user name" from XP to work
at all.  I can only ever connect as the user I'm logged on to the XP
system as.  I want to connect as a different user to one particular
share so I don't have to open up the write permissions.

Has anyone else used this and got it to work?

When I try "Connect using a different user name" I enter a valid samba
user and password but it always fails and asks for the user name and
password again.  Even if I enter the user name that I already am in
the boxes it fails.  Does the user name need some sort of domain
prefix or something?

-- 
Chris Green