In that case I think you can log in as root by simply booting to recovery with no password needed.
When you get the prompt run;
Code:
cat /var/log/auth.log | grep sudo
This should cast some light on the problem.
You may want to take a look at /etc/group to make sure you are still in the sudoers group.
The gratuitous # would be the place to reset your password too.
If you can't figure out anything else this would also be the place to create a new user.