Win98 loggin’ to a NT4 domain

Hi all,
I have a big problem with some Win98 clients I have in my Lan. The fact is that I never had problems like these; I formatted two of them, and now they don’t get policies anymore. I mean, when you switch the PC on it looks for usernames and passwords, but it performs operations that with certain accounts should be forbidden. Moreover, there’s an alert script coming from the server, but these two computers don’t receive it. The configuration of the network should be ok: fixed IP, WINS isthe server, Gateway and DNS is the router.
What should I check more?
Please help if you can, because it’an urgent thing.
Bye, Fabio Casale

P.S. sorry for the lenght of the post