Virtualbox Guest Additions problems in Sabayon Linux 5.3

I'm running Sabayon Linux 5.3 in Virtualbox (Windows Host). I've heard that Sabayon Linux comes with the Virtualbox Guest Additions as part of the system, but only Mouse Pointer integration is working. I've tried installing the Guest Additions manually, but I can't because the installation says that I already have a version installed. It did ask me if I still want to continue the installation, but the installation was canceled before I could type "Yes" or "No". How do I get all of the Guest Additions Features working?