Get: VirtualBox-3.1.6-59338-SunOS.tar.gz
Get: VBoz.zip

Unzip and RENAME python-lib-3.1.8.tar.bz2 TO python-lib.tar.bz2

Put everything in the same dir.

VirtualBox-3.1.6-59338-SunOS.tar.gz
solaris-lib.tar.bz2
sunwvbox-1.0-20100217.diff.gz
python-lib.tar.bz2

And now:

# add required packages
aptitude install alien g11n-minimal-uiu8 lib64gcc1 lib64stdc++6 lib64z1 libfontconfig1 libfreetype6 libgcc1 libice6 libpng12-0 libsm6 libstdc++6 libxau6 libxdmcp6 libxmuu1 libxrender1 python python-dev sunwcsl sunwcslr sunwlibm zlib1g

# untar & prepare VirtualBox
tar -xzf VirtualBox-3.1.6-59338-SunOS.tar.gz
alien -d -s -c --reloc_root=/ VirtualBox-3.1.6-SunOS-r59338.pkg

# patch it
gzip -d -c sunwvbox-1.0-20100217.diff.gz | patch -p0

# build it
cd sunwvbox-1.0
./debian/rules binary

# install the .deb package
cd ..
dpkg -i sunwvbox_1.0-1_solaris-i386.deb

That’s it! Many thanks to Ernst Gill!

SOURCES:
http://www.nexenta.org/boards/1/topics/142