registry.getUserNotifier().notifyError("Thumbnail Retrieval Failure", s, exc);
    public void handleException(Throwable exc)     {        String s = "Thumbnail Retrieval Failure: ";        registry.getLogger().error(this, s+exc);        registry.getUserNotifier().notifyError("Thumbnail Retrieval Failure",                                                s, exc);        viewer.setThumbnail(null);    }