Just so I know I understand you, you have the MIDI IN and OUT on the PC connected to the MIDI OUT and IN on the Clavinova. Are you trying to record MIDI using Cakewalk ? Cakewalk shouldn't be waiting for any sync in that case and would be running using the internal PC clock. If you are trying to record asn external sequence then Cakewalk should be in slave clock mode and once put in record mode, will wait for the external sequencer to start running and sending MIDI clock.