The following tests in MemoryLeakTestCase fail when run with IBM JDK 1.6:
testPropertyUtilsBean_descriptorsCache_memoryLeak()
testPropertyUtilsBean_mappedDescriptorsCache_memoryLeak()
testWrapDynaClass_dynaClasses_memoryLeak()
See http://commons.markmail.org/message/gogzevkklnqwrrc2
Just as a NOTE - those tests also fail using Sun's JDK versions 1.3 and 1.4 (the tests don't execute unless the JDK version is 1.5+)