What have I done??? Double-click arms record *resolved*

I have no idea what I’ve done but all of a sudden double clicking a MIDI track no longer opens up the MIDI editor it now arms the track for recording. How have I managed to do that and how do I undo it? Facepalm What’s going on???

edit
Oh and going to Menu > MIDI > Open Key Editor does nothing at all but Score and List work fine. :confused:

Ok it seems to be sorted now. I shutdown Cubase and rebooted it without the CC121 switched on and it was ok so restarted it again with the CC121 an dit still seems alright. Hopefully it won’t become a regular thing.