On o.S11.4 NX client cannot connect to X server

until 2 weeks ago I had o.S11.3 on both my Siemens and Asus laptops.
I have installed NX No Machine. ( I know it’s not open source,I am using the free version).
With commandline ( root) /usr/NX/bin/nxclient I was able to connect to the other machines.
I got Qt: Locales not supported on X server, the NX menu popped up
and I was able to connect by inserting resp codes.

After fresh install of o.S.11.4 on the ASUS the commandline (root) answers:
xlib: connection to":0.0" refused by server
xlib: No protocol specified
nxclient: cannot connect to X server:0.0
The ASUS can still be reached from the other machines (one with o.S.11.3,the third one with o.S.11.2 )
SSH ( Lan)connections are all working forth and back between the machines, even to and from Win XP, however only from Win 7 on the ASUS, but that’s a Win7problem.

Comparing the installed xorg-x11- server-extra : on o.S. 11.3 Additional
X servers ( Xmdx,Xephir,Xnest,Xvfb ) ,on o.S.11.4 the Xvfb is missing, might that be the reason? If not, I’am sorry for the wrong question.
Thanks E.K.

eventually having solved my problem to use NX nomachine from o.S-11.4:
commandline: <user@linux-…>:ssh -X <iPnumber>
Last login:<Date …iPnumber… Have a lot of fun…
<user@linux-…>:su -
linux-…:~ # /usr/NX/bin/nxclient
after the last input The Nomachine menu pops up and is ready for use.