Comment 2 for bug 238623

though this is probably more suited as a question than a bug report I will leave it to you or a triager to make that conversion.

(sudo: unable to resolve host lamaquina) indicates your host name in /etc/hosts doesnt match your hostname in /etc/hostname.

To resolve that issue change /etc/hosts and remove any suffixes to the hostname. starting in early alpha of ubuntu 8.04 this has been an issue. It is probably best to do this from a root login (recovery mode)

Once you have done this the sudo problems should disappear.