Re: This is not a TikiWiki file. Check if this file was uploaded and if it is dangerous.
Have you uploaded the tiki-secdb_1.9_mysql.sql file into your database already? It contains the CRCs to all tiki php files. You can do that on tiki-install.php.
By default it should complain only about local.php (because everyone has a different one with his own database parameters) and tiki-install.php, if you disabled that file in the install process (tiki uncomments some lines then -> CRC changes).