I just started playing KSP again after a bit of a hiatus, and I updated MechJeb after realizing my version no longer worked. I downloaded the most recent version from Jenkins, Build #257. I put the MechJeb2 folder in the GameData folder and I tried putting the files directly in the folders they are supposed to go in. Yet, whenever I opened the game, I never saw an interface for MechJeb even after placing the AR202 on a craft. If I right-click on the AR202 I get the options to "control from here" or to rename the vessel, so I think at least some part of the mod is working. I just don't have an interface.