Hello,
could you please specify which protocol you use when you try to connect to the problematic server? Is it NX or SSH? In any case, please send us /usr/NX/var/log/nxerror.log from the server and compressed $HOME/.nx from client, after reproducing the issue. Before you try to reproduce the problem please make sure that client will not remove logs after you close it. To do so open the Player and go to Preferences -> Appearance and check “Don’t delete old log files on exit”.
Thank you.