Unix services for windows & Linux\Red Hat

I am not too familiar with linux, so please keep that in mind while reading this post. We have a few linux servers joined to the domain, and linux services for windows running. I have a user that can connect to one linux server, but not another.

I ran the cat /etc/passwrd and noticed the user was not listed on either server... again he can access one server but not the other, and no account specified. I have vnc'd into each server and ran system-config-users command and added a local account.

My questions are?
Since I used his UID from AD Unix service when I setup accounts on each linux server will that sync up his password? If not, what did I miss?

Why could he connect to one server, but not other? I am sure that this vague, again I am newbie to linux.