Country : (unidentified) GEOIP_COUNTRY_CODE

I built a tracking program for visitors on a network of sites. I noticed that I see about 20% of users from a decent pool of ip addresses, coming from an unidentified country known as "--" which is what php will input into the database when I call for the users country.

the Server Global
$_SERVER['GEOIP_COUNTRY_CODE']

How could it not track all countries? is there anything I'd need to up date? I have the latest PHP software on server.

Thank You for your help.

I've been doing some research at what this really was. and it seems it is a API Library from MaxMind

http://www.maxmind.com/app/mod_geoip

directed from php group

http://www.php.net/manual/en/geoip.requirements.php

Which I had no idea they used a 3rd party library. So I will look into updating that. If anyone has other notes or answers to GEO variables using IP, please post. Thanks