I installed pecl geoip feature, and everything is working now,
I run the script geoipUpdateRows.php in order to regenerate geoip data, and it ended saying:
Now that you've geolocated your old visits, you need to force your reports to be re-processed. See this FAQ entry: http : //piwik.org/faq/how-to/#faq_59
Following faq 59, I deleted (with phpmysql) all the piwik_archive_* tables,
In a few hours I got all the old reports regenerated, but not the weekly reports: In the “Evolution over the period” monthly graph, only the last 2 weeks has been regenerated, while preceeding ones are all at 0; and this despite that daily, monthly and yearly graphs correctly show all the values for all the months (about 19) piwik is collecting data.
The archive log doesn’t show any error.
I tried adding to the file config/config.ini.php the lines