I am using V8.2 of NSM and do not have an issue with Java. Some of the pages that use Java are slow to load, but normally load after a minute or so. I'm using the latest Chrome browser with NPAPI support enabled which allow it to run Java. I'm running the latest version of Java on my client.
From NSM V8.3 Java applets will no longer be used in the GUI which should resolve the issue.
Review the below KB on McAfee Support for more details