I've installed Ubuntu 14.04 LTS in an Oracle VM Virtualbox on an HP Pavilion laptop. When I start it, I get a logon screen, but when I logon it just hangs with a blank purple screen.
I tried the advice at http://turriebuntu.wordpress.com/general-ubuntu-pages/ubuntu-boot-freeze-lockup-it-stops-with-a-blank-purple-or-black-screen/ -- intercepted the boot sequence and entered
nomodeset but it made no difference (although that was for a different version, and I suspect getting to the logon screen means I'd already got past that point).
What's a Linux/Ubuntu novice to do to actually get into Ubuntu?