Help i can’t get access to sudo!

I keep getting the error when I type sudo
sudo: must be setuid root
I did ls -l /usr/bin/sudo
and got
-rwxr-xr-x 2 root www-data 127668 2011-01-19 18:01 /usr/bin/sudo
how do I permissions again! I want to access my website ((
I can’t even replace in ftp because I don’t have access.
I did this stupid command
sudo usermod -a -G www-data root
Answer #1
Dont use sudo.
Type: su <enter>
put your root password and then you can do anything you want.
Then if you want you can edit the file sudoers under /etc/sudoers to fit your permissions. Here is a sample file with some common cases:http://www.gratisoft.us/sudo/sample.sudoers
Answer #2
i get an error when put su then my pass