Good news: GeoIP is now integrated in Piwik, enabling Accurate Visitors Geolocation in your Analytics reports. To enable GeoIP go to the Settings > Geolocation admin page, and follow the short instructions.
You can also get an even more http://www.maxmind.com/en/geolocation_landing?rId=piwik to enjoy top accuracy in detecting your visitors locations.
See also the documentation about Geolocation - Analytics Reports in Piwik.
MaxMind also provides two free databases that are less accurate than the commercial ones. One of the free databases can only be used to determine an IP address' country. The other, called GeoLite City, can be used to determine the same information as the commercial city database.
A white screen really usually means an error is not logged. can you double check that your php.ini contains the error logging enabled ? Also, maybe you could try to do a fresh install of piwik a new directory and copy config/config.ini.php to it ?
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