Samba is trying to use hostname instead of username

[Jelmer Vernooij]

Hi,

I've just installed samba at a Linux server in a network with about 100 
NT 4 clients. Everything is working fine... except for the password authentication.

I did some research and found out that samba is trying to validate the password together with the HOSTNAME!
Here are some strings that are used as 'username':

lok05pc11
Lok05pc11
lok05pc11
LOK05PC11

lok05pc11 is the hostname of the machine that is trying to log in.

What am I doing wrong? Why is samba checking all these names?

Tia,

Jelmer