squiggle access denied error

When I run squiggle, the application starts a splash-screen called "Java Applet Window", which hangs. It prints the following error to the command line:

java.security.AccessControlException: access denied (java.net.NetPermission setDefaultAuthenticator)
 at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323)
 at java.security.AccessController.checkPermission(AccessController.java:546)
 at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
 at java.net.Authenticator.setDefault(Authenticator.java:110)
 at org.apache.batik.apps.svgbrowser.Main.<init>(Unknown Source)
 at org.apache.batik.apps.svgbrowser.Main.main(Unknown Source)
Exception in thread "main" java.lang.NoClassDefFoundError: org/w3c/dom/svg/SVGDocument
 at java.lang.Class.getDeclaredMethods0(Native Method)
 at java.lang.Class.privateGetDeclaredMethods(Class.java:2427)
 at java.lang.Class.getDeclaredMethod(Class.java:1935)
 at java.awt.Component.isCoalesceEventsOverriden(Component.java:5819)
 at java.awt.Component.access$300(Component.java:168)
 at java.awt.Component$3.run(Component.java:5773)
 at java.awt.Component$3.run(Component.java:5771)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.awt.Component.checkCoalescing(Component.java:5770)
 at java.awt.Component.<init>(Component.java:5739)
 at java.awt.Container.<init>(Container.java:239)
 at java.awt.Window.<init>(Window.java:413)
 at java.awt.Frame.<init>(Frame.java:403)
 at java.awt.Frame.<init>(Frame.java:368)
 at javax.swing.JFrame.<init>(JFrame.java:163)
 at org.apache.batik.apps.svgbrowser.JSVGViewerFrame.<init>(Unknown Source)
 at org.apache.batik.apps.svgbrowser.Main.<init>(Unknown Source)
 at org.apache.batik.apps.svgbrowser.Main.main(Unknown Source)
Caused by: java.lang.ClassNotFoundException: org.w3c.dom.svg.SVGDocument
 at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
 at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
 at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
 ... 18 more

On the internet, I find more people with the same error (on different operating systems), but I can't find a solution. It seems to have to do with Java's security settings, but I don't understand about these, and I never touched them.

Xubuntu 8.10
sun-java6-jre (6-10-0ubuntu2)
libbatik-java (1.7dfsg-0ubuntu1)