Unfortunately you don't provide enough information in your question, to this fairly generic issue.
It could be that you do not have the additional NFS client installed on your Windows systems.
It could be that you support both SMB and NFS on your file server and your working clients have a different provider order configured in their networking stack to your non-working clients (SMB vs. NFS).
You can troubleshoot this further from the command line:
- to check/mount NFS:
C:\> showmount -e server_name_or_IP
C:\> mount -o anon server:\share *
- to mount SMB:
C:\> net use * \\server\share /user:<username> <password>
It could be that your NFS share is only exported to a select number of hosts, so some hosts can not connect, since they are not in the NFS export list.
If you are running Windows 7 clients, it could be an anonymous GUI mismatch, see:
Anyway, try that for a start and see how you go..