RapidMiner.init() goes wrong

Hi there,

I''m using the 5.0 version. The code isn't complex so far:

RapidMiner.init();

and the error is following:

Exception in thread "main" java.lang.AssertionError
        at com.rapidminer.operator.ports.impl.InputPortImpl.receiveMD(InputPortImpl.java:76)
        at com.rapidminer.operator.ports.metadata.SimplePrecondition.assumeSatisfied(SimplePrecondition.java:90)
        at com.rapidminer.operator.Operator.assumePreconditionsSatisfied(Operator.java:1855)
        at com.rapidminer.operator.OperatorChain.assumePreconditionsSatisfied(OperatorChain.java:495)
        at com.rapidminer.tools.OperatorService.registerOperator(OperatorService.java:414)
        at com.rapidminer.tools.OperatorService.parseOperators(OperatorService.java:283)
        at com.rapidminer.tools.OperatorService.parseOperators(OperatorService.java:279)
        at com.rapidminer.tools.OperatorService.parseOperators(OperatorService.java:279)
        at com.rapidminer.tools.OperatorService.parseOperators(OperatorService.java:279)
        at com.rapidminer.tools.OperatorService.parseOperators(OperatorService.java:255)
        at com.rapidminer.tools.OperatorService.registerOperators(OperatorService.java:229)
        at com.rapidminer.tools.OperatorService.registerOperators(OperatorService.java:203)
        at com.rapidminer.tools.OperatorService.init(OperatorService.java:149)
        at com.rapidminer.RapidMiner.init(RapidMiner.java:388)
        at pl.maliniak.poker.db.Test.main(Test.java:124)
Java Result: 1

As you probably have guessed I'm new to RM. All I want to do is to use a model built with GUI in my Java code. I guess I'm missing something basic. Any hints would be highly appreciable.