There is a user in #kubuntu-de at the moment who upgraded from Gutsy to Hardy and did nothing manually to her /etc/hosts or /etc/hostname. After the upgrade sudo stopped working for her. The hostname was still maxi as before the upgrade, but the line in /etc/hosts suddenly said 127.0.0.1 maxl (small L in the end). How that lower case L got there is a mystery. After logging in with recovery mode and changing it to an i, sudo is working again as expected.
There is a user in #kubuntu-de at the moment who upgraded from Gutsy to Hardy and did nothing manually to her /etc/hosts or /etc/hostname. After the upgrade sudo stopped working for her. The hostname was still maxi as before the upgrade, but the line in /etc/hosts suddenly said 127.0.0.1 maxl (small L in the end). How that lower case L got there is a mystery. After logging in with recovery mode and changing it to an i, sudo is working again as expected.