One client has problems, the other clients are operating normally, but ypbind is running on the problem client. The client might have an incorrectly set domain.
On the client, run the domainname command to see which domain name is set.
client7# domainname neverland.com
Client7# ls /var/yp...
-rwxr-xr-x 1 root Makefile drwxr-xr-x 2 root binding drwx------ 2 root doc.com ...
If the domain name returned by running domainname on a machine is not the same as the server domain name listed as a directory in /var/yp, the domain name specified in the machine's /etc/defaultdomain file is incorrect. Log in as superuser and correct the client's domain name in the machine's /etc/defaultdomain file. This assures that the domain name is correct every time the machine boots. Now reboot the machine.
The domain name is case-sensitive.