On http://www.puppygames.net/applets/titanattacks.jnlp using windows xp on jre 5.0.8 I got

java.lang.NullPointerException
   at net.puppygames.applet.Game.exit(Game.java:932)
   at net.puppygames.applet.Launcher.main(Launcher.java:70)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
   at java.lang.reflect.Method.invoke(Unknown Source)
   at com.sun.javaws.Launcher.executeApplication(Unknown Source)
   at com.sun.javaws.Launcher.executeMainClass(Unknown Source)
   at com.sun.javaws.Launcher.continueLaunch(Unknown Source)
   at com.sun.javaws.Launcher.handleApplicationDesc(Unknown Source)
   at com.sun.javaws.Launcher.handleLaunchFile(Unknown Source)
   at com.sun.javaws.Launcher.run(Unknown Source)
   at java.lang.Thread.run(Unknown Source)