Just recently installed Ubuntu 10.10 in Virtualbox on a Windows host (Vista 64 bit) successfully after an initial hurdle related to RAM.

I've run into a problem regarding writing data files on USB. It appears that I have permissions problem and I am unable to write any file to a USB mounted, even if I wipe and reformat the USB.

There has been a thread on this forum already - http://ubuntuforums.org/showthread.php?t=1365287 but the information is outdated and the manage groups option no longer exists. Can I have any help on this?

(I have already enabled the Virtual Box drivers in System Settings --> Additional Drivers but USB support is still unavailable. I have also tried
sudo usermod -a -G vboxusers jacob
but it says that
usermod: group 'vboxusers' does not exist

Thanks in advance.