Acabo de instalar o JDK 1.5 (estava usando 1.4.2_07) e o JasperReport (0.6.4) não funciona mais.
Aparece o seguinte erro:
cannot access java.lang.Object
bad class file: C:\Arquivos de programas\Java\jre1.5.0_01\lib\rt.jar(java/lang/Object.class)
class file has wrong version 49.0, should be 48.0
Please remove or make sure it appears in the correct subdirectory of the classpath.