0.23.5 MechJeb does not work for me. I extracted the MechJeb2 folder into the GameData folder as required, downloaded from: http://jenkins.mumech.com/job/MechJeb2/ so I had the latest update. But nothing worked. The side menu was there, but even with the mechjeb instrument attached to my craft - when clicking on the mechjeb side menu - nothing appeared. It slides out, but there is nothing to click on. I've tried around a dozen different ways now, and to my avail, a similar outcome was all that I received for my endeavour.