Wurst 1.0 crashed for some people because it required Java 7. If it crashed for you, that means you still have the old Java 6 and you should update to Java 7. Wurst 1.0.1 will work with Java 6 again, but having an old version of Java is always bad and will cause many Java programs to crash. AltChecker also requires Java 7, but that won’t change because it uses the new features in Java 7.