Connection Failed Error on all terminals

Connection Failed Error on all terminals

we have a school with a small computer lab with 30 Wyse VXO terminals connected to a Windows 2003 server. The lab has been operational for the past 4 years connecting perfectly. A couple of weeks ago several of the terminals began giving us the error message "Connection Failed" but many of the others were still working. Then last week, all the remaining terminals began saying the same thing "Connection Failed" and none of the workstation terminals will connect at this point.

I checked and verified that the IP addres and DHCP info was being configured in the terminals but cant figure out why they all have stopped connecting to the 2003 server.

we can ping the terminals/workstations from the server and get replies back but cant seem to get the terminals to ping the server, the terminals can however, ping the common (server and terminasl) gateway (everything is on the same LAN)

Any troubleshooting suggestions would be welcome!