Going from version 3 to 4 is quite a change and there's a lot of
difference so your VM's may not port over. I started afresh with
version 4 when installing 12.04 this time. If you find they don't then
you can go back to version 3 if you've still got the installer files
of course ( I have 64bit installers 3.2 and both 32bit and 64bit for
version 3.1 if you get stuck ).