I am using Batik with Java 6. I have to use the batik-ext.jar because some of the classes in the library are used by some batik classes (like KeyboardEvent). Other classes of the batik-ext.jar are already part of the Java 6 Runtime (like EventTarget). So on runtime, there are conflicts between dublicate classes. My workaround: I opened the batik-ext.jar and deleted all duplicate files. If you have a better solution to solve my problem, please say it to me. PS: It was not so easy to recognize that the reported exception was a result of the descripted problem. ;)