One PC cannot access others on network

I have a home network.
An XP Pro desktop is the master. I have another desktop with Win 2000 Pro
plus two laptops both running XP Pro.
The two laptops connect wireless. The wireless router is a D-Link 524.
All connect to the internet with no problem.
One laptop can see and access all the shared files and shared printers on
the main computer through the wireless connection which was the whole point
of this network.

The Win 2000 pc also accesses all shared resources on the master.

The master computer, however, cannot access the other two although it can
see them as part of the network. Message is “you may not have rights etc�.

The specific drives and folders on the laptop and the Win 2000 pc are
shared. TCP/IP protocol is of course installed as usual. I have also
installed netbui on all the computers as suggested in one post.

I am running ZoneAlarm Pro firewall on the master and have included in the
trusted zone the ip addresses of the other computers.

If anybody has anything else to try please let me know.
Cheers