The ebuild for app-emulation/virtualbox-bin-4.0.0 needs to set the permissions of the VBoxExtPackHelperApp program (usually installed in /opt/VirtualBox ) to executable, and possibly also SUID root. Owner/group should be root:vboxusers. Without this program set as executable, extensions cannot be installed into VirtualBox. Reproducible: Always Steps to Reproduce: 1. Install virtualbox-bin-4.0.0 2. Attempt to install the Extensions Pack from http://www.virtualbox.org/wiki/Downloads 3. Installation fails because VBoxExtPackHelperApp cannot be executed.
Why dont you use the extenstions ebuild? app-emulation/virtualbox-extpack-oracle
This has been fixed meanwhile.