I know it's not a solution, but, if you have a USB key somewhere, download the latest image at http://cdimage.ubuntu.com/daily-live/current/ open up the USB startup disk creator from the Administration menu, hit 'erase disk', select as much as possible of extra space and click 'make startup disk'. It' *much much* nicer than virtualbox
I'm using a USB disk every day to develop software for Unity, it's a pretty rocking way to run Unity.