Okay, look, the issue that's causing the issue you described in the OP, if what you've told me so far is correct, is being caused by one of your add-ons. So, what that means is, one of your add-ons is making the game crash. You do not have to delete any folders, you don't have to reinstall blockland.
All you have to do is find the perpetrating add-on. You can do this by disabling a few add-ons, starting a game, and seeing if it still crashes. If it crashes, you have not disabled the perpetrating add-on. If it does not crash, you have disabled the perpetrating add-on.