Моя версия FreeNX:

NXSERVER — Version 3.2.0-74-SVN OS (GPL, using backend: 3.4.0)

Смотрим в лог, что происходит, когда клиенты не могут подключиться, выдавая сообщение session restore failed, /var/log/nxserver.log:

server_nxnode_echo: NX> 702 Proxy IP: terminal
server_nxnode_echo: NX> 706 Agent cookie: a0b20bdd93f2def43949327536a5e07c
server_nxnode_echo: NX> 704 Session cache: unix-application
server_nxnode_echo: NX> 707 SSL tunneling: 0
server_nxnode_echo: NX> 596 Error: Session restore failed. Reason was: Session: Display failure detected at 'Tue Sep 6 12:05:44 2011'.
server_nxnode_echo: NX> 1005 Session status: suspended
nxnode_reader: NX> 1001 Bye.

Добавляем в /usr/bin/nxserver:

available="$(getparam status)"

Сюда:

else
                                # only unix-* sessions can be resumed, but other session types can still be terminated
                                stringinstring "unix-" "$4" || available="N/A"
                                # Sergei_T
                                available="$(getparam status)"
                                printf "%-7s %-16s %32s %8s %5s %-14s %-11s %s\n" "$(getparam display)" "$(getparam type)" "$(getparam sessionId)" "$options" "$depth" "$geom" "$available" "$(getparam sessionName)" >> $TMPFILE
                        fi
                fi

bugs.launchpad.net/freenx-server/+bug/589723/comments/22