Have installed version 6.6.8 free version, connection to one machine times out.
It is a Windows 7 machine and what can see in the nxservice.log
4944 4948 11:44:48 213 nxexecExecServer: Info: Server process running with pid 4964.
2840 3308 11:44:48 313.021 nxserviceRunEventLoop: ERROR! Read failed.
2840 3308 11:44:48 313.021 nxserviceRunEventLoop: Error is 32, ‘Broken pipe’.
2840 3308 11:44:48 313.021 nxserviceRunEventLoop: ERROR! Too much failures in session [0].
2840 3308 11:44:48 313.021 nxserviceRunEventLoop: checkNxserver failed.