This happens with piwik 15.0 with GeoIP (PHP).
In my effort to recover the lost data (thanks to your help, I managed to recover most of the data, and I think I can forget about what is lost), I did the following.
cp -a pathtopiwik pathtopiwikrecovery
Then I run a second instance of mysqld at port 3307, changed confing.ini.php accordingly, added vhost in apache configuration file, changed DNS setting at domain name provider etc etc to run a second instance of piwik for data recovery.
Geolocation in the original copy of piwik is working fine. However, when I did Administration -> Settings -> Geolocation in the “recovery copy” of piwik, I get these warnings.
WARNING: /srv/http/betc/piwikrecovery/core/Common.php(589): Warning - mt_srand() expects parameter 1 to be integer, float given - Piwik 2.15.0 - Please report this message in the Piwik forums: http://forum.piwik.org (please do a search first as it might have been reported already)
Furthermore the page says that GeoIP (PHP) is broken.
Any idea on what is going wrong here?