As I have previously mentioned, my employer uses thin clients in some locations. They’re cheap, and they usually just work. They are, of course, dependent on a network connection to the server to work.
When the server connection is not there, for whatever reason, the error they serve us is the somewhat cryptic “Protocol driver error”. The error message basically tells us that the thin client is unable to acquire an IP-address.
Troubleshoot this error as you would any other network error. In my experience, the problem is usually a network connection that is not patched properly, but there are various other possibilities.