We recently upgraded our entire network from redhat-5.2 to redhat 6.1, but I could not get NIS to work at all. ypserv started up ok on the NIS server, and ypbind would start on the clients. But when NIS requests were put in by clients, eg. ypcat XXX, nothing would be returned (ypcat would hang). ypserv in full debug would show the request but not show any serving of the requested data. Moreover, as more NIS requests came in from the clients ypserv would spawn more and more job until the server almost ground to a halt. After a few hours of head scratching we eventually tried rebuilding the ypserv RPM using different configure options to the original (RedHat) ones, and now everything is working absolutely perfectly. The configure options we used were simply --enable-yppasswd --enable-ypmake
This should be fixed in the errata RPM, which it would be a good idea to update to, in any case.