Ok, well the tables are empty it seems:
mysql> select * from searchresults;
Empty set (0.01 sec)
mysql> select * from searchresultdetails;
Empty set (0.00 sec)
So I guess it's not saving the data correctly.
As you suggested I added:
# database persistent connection
To 'sp-config-extra.php'. So any ideas why it's not working? Does it matter which user runs the cronjob?