I was running 10.10 64-bit quite happily in VirtualBox 4.0.4 64-bit on Windows-7 Professional 64-bit SP1. This morning I upgraded VBox to the latest 4.0.6; 10.10 still worked just fine. The I did an online upgrade to 11.04 and now the Ubuntu VM will not come up. It just sticks at the Ubuntu screen with a row of dots and that is it.

How can I troubleshoot this so I can get it to boot. I really don't want to have to do a clean install if I can avoid it.

Thanks.