just tried vbox 4.0.8-r71778 under windows with 9front and it seems to install and boot the latest build just fine. (except that vbox seems to measure its performance in popups per minute)
i had some wired i/o errors tho when i had the iso image stored on smb server after some time. maybe a bug in cifsd... just copying the iso to a windows harddrive fixed it. where does plan9 fail to work? can it start the kernel? we use a different bootloader so i would suspect a 9load problem... can you make a screenshot? -- cinap