Exception informs JRE can't find class GroupLayout. This class is part of Java's core packages. However, the class was introduced in Java version 6. Thus, running Wandora with Java 1.5 throws NoClassDefFoundError.
I suggest you update your JRE to Java version 6 and try again. If Java update is not possible, download Wandora application package again.
I have slightly modified the application. Modified Wandora version doesn't use GroupLayout. However, there may be some other features that require Java version 6 as Wandora is developed with JDK version 6 and there is no separate adaptation process for Java 1.5.