applets grants permission in Netscape

I wrote a applet and want to grant permission to read property.
I add the following code.
netscape.security.PrivilegeManager.enablePrivilege("UniversalProperty read);

Then I use System.getProperty("user.home").
When I run the applet, I see a dialog box asking me to grant or deny permission.( Because I haven't signed my applet, it said my is not digitally signed). Then I pressed grant button.
But when running the getProperty statement. The following error
occurs

# Applet exception: security.checkpropsaccess.key

netscape.security.AppletSecurityException: security.checkpropsaccess.key

  at java.lang.Throwable.<init>(Compiled Code)

  at java.lang.Exception.<init>(Compiled Code)

  at java.lang.RuntimeException.<init>(Compiled Code)

  at java.lang.SecurityException.<init>(Compiled Code)

  at netscape.security.AppletSecurityException.<init>(Compiled Code)

  at netscape.security.AppletSecurityException.<init>(Compiled Code)

  at netscape.security.AppletSecurity.checkPropertyAccess(Compiled Code)

  at java.lang.SecurityManager.checkPropertyAccess(Compiled Code)

* at java.lang.System.getProperty(Compiled Code)

  at Capture.run(Compiled Code)

  at java.lang.Thread.run(Compiled Code)

java.io.IOException: CreateProcess: vcafe -netscape error=2

  at java.lang.Win32Process.<init>(Compiled Code)

  at java.lang.Runtime.exec(Compiled Code)

* at java.lang.Runtime.exec(Compiled Code)

  at netscape.debug.Debugger.launchDebugger(Compiled Code)

  at netscape.debug.Debugger.uncaughtException(Compiled Code)

  at netscape.applet.AppletThreadGroup.uncaughtException(Compiled Code)


What's the problem?

ALso, netscape's JVM has java.security package?