[CentOS] ssh -Y X-forwarding?

On rare occasions I want to run a remote X command (like 'meld' to
interactively merge changes in files) and normally 'ssh -Y
remote_host' from a terminal in an NX/freenx window that is acting as
my desktop to start and any X program subsequently started would open
in a new window via X-forwarding - at least when the target is a 5.x
host.  I don't do it often enough to remember if it ever worked when
the remote side is 6.x, but today it is not setting the $DISPLAY
variable, so I get:
Error:  Can't open display:
Using -vv shows it at least trying to go through the motions:

debug2: x11_get_proto: /usr/bin/xauth  list :1420.0 2>/dev/null
debug1: Requesting X11 forwarding with authentication spoofing.
debug2: channel 0: request x11-req confirm 0
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
debug2: channel 0: request env confirm 0
debug2: channel 0: request shell confirm 1
debug2: fd 3 setting TCP_NODELAY

But, $DISPLAY is not set to anything.   What am I missing?

--
   Les Mikesell
     lesmikesell at gmail.com