Perhaps I may be of assistance.
Windows 98 can not actually be a "member" of a Domain because it does not
have a built-in security system that can establish a secure link to the
Domain Controllers, but it CAN participate to some degree in Domain based
security.
On the Windows 98 computer, look in Control Panel, Network, select the
Access Control tab. Is the "User-level access control" radio button
selected with the name of the Domain in the "Obtain list of users and groups
from:" text box?
If so, this means that any person connecting to anything shared from this
computer must have thier Domain User Account specifically permitted to
actually connect to that share.
At this time, I don't have a Windows 98 computer available to experiment
with (I hope to get Windows 98 installed in a Virtual Machine so I can see
exactly the dialogs involved).
When you create a folder share on Windows 98 computer that is participating
in Domain security, on the Sharing tab of the folder's Properties, there is
a list of who is permitted to connect to that share and an Add button. You
use the Add button to add Domain User accounts or Groups to the list so that
they can connect to the share. If I recall correctly, it is the same for
shared Printers, although the dialog may be different.
See if this makes any sense at all and post back (maybe by then I'll have a
Windows 98 installation!).