I can’t understand why just OS X clients would have the problem & not Windows or Linux? I thought the Nomachine client was the same cross-platform. However, I’ve just verified that it does work fine with a Windows client, so I’m not sure what’s going on here either.
On the contrary, I’m sure that I don’t know what’s going on here but we noticed that it happens. That OS X client doesn’t like the Gnome version in 11.4. It’s doing fine with Gnome on 11.3 and with KDE on 11.4. But you can try to update the NoMachine client on your Mac. Maybe it will help.
I have the latest version, 3.4.0-8 at the time of this writing.