samba - Dec 2003 - Problems joining a Domain

I've upgraded my Domain from 2.27a to 3.0. My authentication is done using
the standard smbpasswd file. Since I've upgraded to 3.0, when I try to
join a XP machine to the Domain, I get unknown user or password message.
I'm using add machine script that's found in the Doc for Samba 3.0.

I running Fedora Core 1

I use the following scripts:
	add user script = adduser -u
	delete user script = userdel -u
	add machine script = /usr/sbin/useradd -d /dev/null -g 100 \{} -s
/bin/false -M %u


I'd be grateful is someone could point me in the right direction.

Thanks

Roberto