But it is a little bit strange that jBPM throws this exception when there is an access to the process variable application. The error doesn't occur when the java activity is running. The Java task doesn't have any problems. But if the classpath is wrong, the problem should occur in the java activity and jBPM shouldn't come to the task. Am I thinking right? So I would say that the class path is ok, but obiviously not. Any ideas?