I've had a problem with mechjeb today. I've had the mod working just fine with the game since .21 came out, I have the most up to date version of the game and the mod. Mechjeb just stopped working all of a sudden. The tab on the right side of the screen no longer appears when I attach the mechjeb part to a craft. I tried reverting my game folder to it's original state, didn't work; I tried the patch version on this thread as well as the version found at the Spaceport. I have changed nothing, it just decided to stop working. Has anybody had a problem similar to this? This has never happened to me with mechjeb or any other mod. I appreciate the help if somebody knows what's going on. Edit: Fixed it. It was my anti-virus. Comodo Internet security updated its programming today and made my computer reboot, that's when MJ stopped showing up. I should have realized. Apparently the av was identifying MJ files as invalid certificates, and it wouldn't allow me to whitelist the files, only .exe files for some reason. When I disabled the program in startup, it sought revenge and killed my internet connection too, so off to the depths of space goes that anti-virus. I'll leave this up as I'm sure that I'm not the only one using MJ and Comodo Internet Security.