Upgrading an OpenSolaris Guest for Virtual Box 2.2

Virtual Box 2.2 was just released. I was rather excited to try Compiz in a box, but was soon disappointed to find that my guest OS could not start properly. After some tinkering, I booted into single-user mode (hit e on the text boot line, then add -s at the end of the kernel$ line, then hit b to boot), and ran pkgrm SUNWvboxguest to remove the old guest additions, which allowed the guest OS to boot up just fine.