DOS Session and 95 – KeyBoard Dead

We’ve several machines that have developed the same symptom: Open a MSDOS window/session and the keyboard will not work. We’ve virus checked, copied in command.com from a working machine, etc. Problem continues. Any suggestions, anybody else seen this. We’ve recently changed our Novell network to Ethernet from Token Ring .. the rest of our world (on these machines) has been stable? Thanks ahead of time .. Jp. Maritn