Can you run the cracker through the console? That may offer you a stacktrace which I can use to debug the problem.
To do this,
1. Open a command prompt
2. Move to the directory where your EggCrack JAR is ("cd C:\Users\You\etc")
3. Run "java -jar EggCrack.jar" where "EggCrack.jar" is the name of the JAR that contains the application
4. Read output, post here
Thanks