Its come to my attention that the GeoIP.dat included with SM releases/snapshots are not updated, and have not been for quite a while.
I attached a new version to the OP that should help/eliminate "Unknown" location errors, just download and upload it, you will most likely have to restart your server to install it.
You can also get the latest binary version from here:
http://www.maxmind.com/app/geoip_country
It's currently the same as the attached version.
I'm going to start including the latest GeoIP.dat within the plugin release file, just make sure you don't overwrite the new version with SM's old one when you update your SM build.
-I'm going to try to get them to include an updated file.