Hi everyone. I got it working, and I'am glad and a bit embaressed, because I just discovered that 3D acceleration isn't ENABLED in virtualbox by default and I didn't enabled it. :D What's even worse, it say'd so in the (very short and easy to read) manual. So RTFM is in effect here...
But anyway, vboxvideo is the driver you need to use. It abstracts the nvidia driver from the host system AFTER you installed the guest additions. -- This message posted from opensolaris.org