windows 98 SEC join Windows 2003 domain

Hi, there,
I have a curious networking problem on the windows 98 sec pc to join windows
2003domain. We only have one 2003 SBS server with SP1, DNS, DHCP, and WINS
also installed on this server to server company user. some client is still
using windows 98 SEC, some use XP or 2K. And this is also a file server for
user.

I configure the windows 98 pc use DHCP for IP, and WINS for Naming
resolution(which is the only server IP address), defualt gateway and subnet
mask also configure without any problem. The problem is, the win98 user can
not access the shared folder on the server some times, if try to access the
mapped folder from the desktop, will pop up a window for passwork to access
this folder, if try to access the server from the network neighbourhood, it
will give err msg of "access is denied", even in this case, I can still ping
to server, and can access internet without any problem, after restart the pc.
everything works fine.

All windows 2k and xp have no problem on such issue.

where did I do wrongly?

Thanks for any suggestion on this.

Rgds
Shermaine