ERROR: When trying to accept digita signature!

[Felipe Menes]

When I try to execute an applet with IE, the folowing error occurs:

 sun.misc.ExtensionInstallationException: IO Error. Unable to verify optional package installer.
 
at sun.plugin.extension.ExtensionInstallationImpl.verifyJar(Unknown Source)
 
at sun.plugin.extension.ExtensionInstallationImpl.access$100(Unknown Source)
 
at sun.plugin.extension.ExtensionInstallationImpl$1.run(Unknown Source)
 
at java.security.AccessController.doPrivileged(Native Method)
 
at sun.plugin.extension.ExtensionInstallationImpl.installExtension(Unknown Source)
 
at sun.misc.ExtensionDependency.installExtension(ExtensionDependency.java:346)
 
at sun.misc.ExtensionDependency.checkExtension(ExtensionDependency.java:183)
 
at sun.misc.ExtensionDependency.checkExtensions(ExtensionDependency.java:150)
 
at sun.misc.ExtensionDependency.checkExtensionsDependencies(ExtensionDependency.java:101)
 
at sun.misc.URLClassPath$JarLoader.parseExtensionsDependencies(URLClassPath.java:825)
 
at sun.misc.URLClassPath$JarLoader.getClassPath(URLClassPath.java:805)
 
at sun.misc.URLClassPath.getLoader(URLClassPath.java:292)
 
at sun.misc.URLClassPath.getResource(URLClassPath.java:159)
 
at java.net.URLClassLoader$1.run(URLClassLoader.java:191)
 
at java.security.AccessController.doPrivileged(Native Method)
 
at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
 
at sun.applet.AppletClassLoader.findClass(AppletClassLoader.java:143)
 
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
 
at sun.applet.AppletClassLoader.loadClass(AppletClassLoader.java:123)
 
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
 
at sun.applet.AppletClassLoader.loadCode(AppletClassLoader.java:561)
 
at sun.applet.AppletPanel.createApplet(AppletPanel.java:619)
 
at sun.plugin.AppletViewer.createApplet(Unknown Source)
 
at sun.applet.AppletPanel.runLoader(AppletPanel.java:548)
 
at sun.applet.AppletPanel.run(AppletPanel.java:299)
 
at java.lang.Thread.run(Thread.java:534)
 

 

It happens even if the Applet is signed, by my own signature and other's.
Please, help!