Check if you have a core dump in the home directory of the user owning the session.
Please also attach the logs files:
# tar zcf logs1.tar.gz /usr/NX/var/log
# tar zcf logs2.tar.gz /home/<user>/.nx
Be sure you include all the information listed here:
– NoMachine product and version on local and remote machine (free version, Workstation, etc).
– Whether the problem arises connecting to a physical or a virtual display.
– Remote and local Windows/Mac/Linux version (Windows XP/7/8, OS X 10.x, Ubuntu xyz, Mint x.y, etc.).
– If on Linux, desktop version (GNOME. KDE, whatever) on client and on server.