Could be a cache issue as some java apps have loathesome cache management and leave bits lying around.
Could be a classpath issue as some java apps package their own JVM.
1. Clear as much cache as your app will let you, including browser cache.
2. Look at your CLASSPATH variable and ensure that it includes a file path reference to the correct version of Java. The CLASSPATH can be configured in 2 places a) OS System settings b) The application launch script. The correct version of Java should be listed at the start of the CLASSPATH
Hope this helps.