I have been using Precise Pangolin and I am into a problem now :( I was trying to add my current user to the group vboxusers.. So I used the command,
sudo usermod -G vboxusers myusername
And it got succeded too. But after adding like that, I am unable to perform any sudo operations. Whenever i use a sudo command I get an error message stating "myusername is not in sudoers file".
I tried enabling root account also. But I couldn't. How to fix this issue?