VirtualBox and X problems when switching user

[mansniks]

Hi!

Recently I installed VirtualBox, it was working ok, but when I created new group NG and user NG to run VB as (because of security considerations), I ran into problems:
1. user NG was added to groups vboxusers, cdrom, users (what is this group for??), but VB still could not acess cdrom device - why?
2. when starting virtual machine, VB freezed on "spawning session"
How to avoid these problems when running VB as another user?

And one more thing - I would be happy if someone knows how to solve:
sudo kwrite /etc/fstab
kwrite: cannot connect to X server

Thank you!

[mansniks]

plz, anybody?