Step 1:
Edit /etc/nsswitch.conf. To do this, open a terminal (programs > accessories > terminal) and copy/paste this command:
Code:
gksudo gedit /etc/nsswitch.conf
Find the line that looks like this:
Code:
hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
And just in front of "dns" add "wins" so it looks like this:
Code:
hosts: files mdns4_minimal [NOTFOUND=return] wins dns mdns4
Save the file, and close gedit.
Step 2:
Install winbind by copying and pasting the following command:
Code:
sudo aptitude install winbind
See if that fixes your problem.
If that still doesn't work, try this: http://ubuntuforums.org/showthread.php?t=288534