So something happend with the latest Netscaler GUI after the last Java Updates. When we tried to open any config changes in the GUI the java applet just wouldn’t load.
Then I discovered that something has changed in the java version, since it containes new parameters. In order to allow the netscaler to load the applet from the browser we have to do some changes to the java gui applet in the control panel.
So we have to remove the keep temporary files on my computer and then restart the browser and voila! 
