Unable to change password logging on W2K

I have a mixed network of Windows 2000 and Windows 98 PCs. I am using Windows 2000 servers. When the Windows 98 PCs have expired passwords, they are prompted to change them, but whne they try, they get a “Unable to change the password for Microsoft Networking because of the following error: Access has been denied.” message. I have checked with Microsofts Knowledge base, but none of the tips I found there worked. Anyone have any ideas?