Any update on this issue? I’m running the Linux client (ubuntu 12.04) and when I connect to a windows server 2008 test VM it doesn’t even have the “special keys” button shown here: https://www.nomachine.com/AR02L00784. Button doesn’t exist.
As a workaround i found I could “attach” my local USB keyboard to the remote server and hit CTRL-ALT-DEL that way, which is neat, but very ugly as it makes switching focus between local and remote system totally suck. I’m evaluating NoMachine for my company and it’s a show-stopper if CTRL-ALT-DEL doesn’t work properly as it does in other remote desktop solutions.