The centre button between the Up/Down/Left/Right arrow buttons is the OK button. On my harmony/MCE remote it pauses and restarts playback all the time. I tested on MC23.0.96 on my HTPC.
I suspect that there is something wrong in your setup Maid. Is it possible to reboot (power down and power up) your remote? i.e. Pull the batteries out, wait a couple of minutes, put them back in and try again. If that doesn't work, put new batteries in it and try again.
I can't replicate the problem I had earlier with Stop dropping back to the Shows menu. I suspect that was a remote control problem, as I had recently updated its settings.