Hello Rob,
thank you :-)
rebuildall.php has successful repaired the search.
To repair the Special:Statistics, I had to do an additional task (information
for archive, etc.):
Because in the database does exist an entry with key=1, the script
init_stats.php cant "INSERT" the values into the table
"wiki_site_stats". So I
droped the first row from the table "wiki_site_stats", and execute
php Init_stats.php again. Success :-)
Regards,
Jan