centos ping problem on some machines

I have centos 5 server. I have 20 computers. All of them plugged into same switch running windows xp. I can ping from 14 of them and 6 wont ping server. I checked the 6 that wont ping the server and there is no firewall. server in at 192.168.1.2. I can ping the gateway which is 192.168.1.1 from those computers. But I cant ping the server. my iptables are turned off. Any help will be appreciated

From serverfault

• 1. You cannot ping by name, or by IP? This'll identify a name resolution issue, if you can ping by IP.
  2. What's the network subnet setting on each machine, and the server? Are they all definitely within the same subnet?
  3. Can you ping the workstations from the server side?
  : i can not ping by ip address. subnet is same all across. cannot ping from the server or to server from those machines
  From Chris Thorpe

• Try running a packet trace while you're attempting to ping. If you run a simultaneous packet trace on the machine and the server and compare the logs, you should get an idea of what is going on.

  From Tristan
• 1. Check if the 6 PCs can ping to/from any other machines within the same LAN.
  2. Check the network card and Ethernet cables of the 6 PCs.
  3. Check the switch port which if it is faulty.
  From Alvin Sim

• Exchange ip address of a non-ping pc with a ok-ping pc. So you can know if the problem is into workstation or into server.

  From lg