I ran into this while trying to help someone over on the UbuntuForums and found a bug report over on launchpad: https://bugs.launchpad.net/ubuntu/+sour ... ug/1014487
I am not sure if this is an Ubuntu problem or a VirtualBox problem, but I've tested it both on my server box and desktop box, both running Ubuntu 12.04 x64.
VirtualBox launches fine and can start VMs fine, but if it it is ran from the terminal, an error of "Error opening file for reading: Permission denied." appears.
It doesn't seem to affect anything but is there a way to track down why this error appears and how to fix it?
There is more info in the launchpad bug report, but let me know if you need more info.