thanks for the fast response.. i reinstalled everything again. clean version! - copied the mechjeb 2.2 #213 into gamedata folder - copied the toolbar 1.7.1 into gamedata folder - starting the game in sandbox mode - building a simple rocket with mechjeb vessel and controller on it (i guess that should be the point where the mechjeb window should pop up?!) in fact, there's no difference to the clean version. i'm clueless! i also got no toolbar.. edit: Problem solved, noobish mistake of mine windows denied the .dll access in program files.. thanks anyway