They released v.24.2 (and v.24.1) to fix a bunch of little bugs- notably the way the game interacts with plugins. Interstellar isn't updated to .24+ yet, but if you are set on playing .24 with interstellar, updating KSP to v.24.2 and reinstalling Interstellar *should* make some things *less* broken. And yea, x64 seems to mess with a lot of things (unity problems).