What I always see is an exception with a stack trace, followed by a 'caused by exception' with a stack trace, and so on. Usually the initial runtime exception is part of the last 'caused by exception' clause. Perhaps if you provide a particular instance where only the message printed, that would help.
Peter your right, I mad the tests you suggested. Sometimes we log.error(e); wich gives back only the exception message. this seams to be my fault. thanks for helping in clarifying