In your /etc/nsswitch.conf file I'd suggest you modify this line:
Code:
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
to look like this:
then reboot your server and see if that fixes the problem.
If that works then you should change the following service in Ubuntu: mDNS/ZeroConf/Bonjour (or whatever it's called), disable or uninstall it as that's causing the problem of the modified nsswitch.conf file. If you do remove it make sure you check the nsswitch.conf file and that it's still set correctly to the new line I've given you above.