If you used the -M option to specify that your request be sent to the master server, and the rpc.nisd daemon has died on that machine, you will get a "server not responding" type error message and no updates will be permitted. (If you did not use the -M option, your request will be automatically routed to a functioning replica server.)
Using uppercase letters in the name of a home directory or host can sometimes cause rpc.nisd to die.
First make sure that the server itself is up and running. If it is, run ps -ef | grep rpc.nisd to see if the daemon is still running.
If the daemon has died, restart it. If rpc.nisd frequently dies, contact your service provider.