So, for some unknown reason, your workstations that were working fine before now are getting a Gateway of 0.0.0.0 IN ADDITION to the proper Gateway, but the default is 0.0.0.0 so they can’t get online.
- Get to a DOS prompt as an Administrator
- Type route delete 0.0.0.0 and hit enter
- Type ipconfig /release and hit enter
- Type ipconfig /renew and hit enter
It may be the Bonjour service causing this. To stop it, use msconfig to stop it from running at startup.
Hope this helps