I have been running my FreeNX for several years with no problem then all of a sudden I tried to log in today and I received a black screen. After several searches I found out that it’s a problem with the window manager temporary files being corrupt. Just to test I changed the settings on my nx client to use another window manager “KDE” in the system and it worked. To resolve the issue I SSHed into the box and deleted all gconfd, orbit and mapping tmp folders/files for the affected user. Tried to reconnect again and it worked.