Thank you for your post.
Deleting the Java cache is a great first step. If Java refuses to launch the applet even after downloading anew, test to make sure Java is working properly at the following URL:
Scenario 1: If the message “Your Java is working” is not displayed, then download and install the latest version of Java.
Scenario 2: If the message “Your Java is working” is displayed, then consider rolling back to a previous version of Java. To do this, uninstall all versions of Java and install Java 6 update 31, a known good version for FileMaker Server 11.