The webalizer shipped with debian lenny is not able to detect the visitor countries. The package "geoip-bin" solves this problem. Maybe this tool is available for other distributions too. But i only know that for debian.
Edit the file "INSTALL_DEBIAN_5.0.txt" and replace "apt-get install vlogger webalizer" with "apt-get install vlogger webalizer geoip-bin"