I have fixed our problem but I have no idea why changing from Java 1.5 to Java 1.6 should case the following error.

org.apache.commons.collections.map.LinkedMap cannot be cast to
java.util.HashMap

The code that was generating the problem was:
Code:
private Map<String, Object> mPropertyEditors = new HashMap<String, Object>();

private void someFunction(Object aObject) {
   Map fieldNames = (HashMap)mPropertyEditors.get(aObject.getClass().getName());
}
under Java 1.5 the mPropertyEditors.get() returned a java.util.LinkedHashMap
under java 1.6 it returns org.apache.commons.collections.map.LinkedMap

Changing the cast to java.util.Map solves the issue but I do not understand why changing to Java 1.6 should cause this change.

Any thoughts ?