K, i installed xubuntu version 6.06 2 days ago and up until 10 mins ago it worked fine. I added a new user and changed my /etc/fstab and after I restarted sudo no longer seems to work. Now the two actions before hand may not have anything to do with it but i said i may as well mention them.
Here's a little example of what i mean
nnp@torvalds:~$ sudo cat /etc/fstab
And yes, the password is correct. Im completely stumped, i've never seen anything like this before.