Platform and Physics aren't designed to work together so won't work well, but it certainly should not crash the editor. I'm afraid it's hard to deal with this kind of issue because there is only the broken project as evidence, which is simply the consequence of the crash, not the problem itself. If you keep backups and can reliably reproduce a crash by some series of steps, do let me know, otherwise it's difficult to do anything about it because there's no information about what caused the crash (and lots of people are adding behaviors every day and it works OK for them). I PM'd you a recovered project, but I had to remove the Physics and Platform behaviors.
It could be your graphics card driver crashed, which is a common problem and not our fault. So maybe try updating them.