After a clean install of RH 6.0, when I first tried to use
ndc, I got the following error messages (these are all with
a cleanly running named, either started by the boot process,
or with /etc/rc.d/init.d/named start):

# ndc restart
ndc: error: name server not running

however, named is running. ndc starts another instance, and
then hangs.

# ndc stop
ndc: error: ctl_client: evConnect(fd 5): Connection refused
ndc: error: cannot connect to command channel (/var/run/ndc)

I took a look at /var/run/ndc, and noticed that the date on
it was earlier than my latest boot, so I stopped named,
moved ndc out of the way, and restarted.  Now ndc works.

The leftover ndc was a pipe, the newly created one a socket.
I don't know where the pipe came from, but the named startup
ought to remove any old /var/run/ndc which is left lying
around.