sudo: unable to resolve host (name already added to /etc/hosts)

Question

Whenever I use sudo, I get this:

sudo: unable to resolve host dave00-G31M-ES2L

Here is my /etc/hosts:

dave00@dave00-G31M-ES2L:~$ cat /etc/hosts
127.0.0.1   localhost
127.0.1.1   dave00-G31M-ES2

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

I logged out/in already. How can I solve this?