You mentioned you are trying to connect to a physical desktop. The logs show that you are reconnecting a custom session.
So first of all, if you want to be sure you connect to the physical desktop, you should create a new connection (you can use the wizard to do this).
As for the reason why the custom session is failing, please give us the output of the following commands executed in a terminal:
1. echo $DISPLAY
2. echo $XAUTHORITY
3. ls -l $HOME/.Xauthority
4. LD_LIBRARY_PATH=/usr/NX/lib /usr/NX/bin/nxauth -f $XAUTHORITY list $DISPLAY