deberas de cambiar la ultima linea:
KEY search (title, caption(255), keywords, filename)
en el tutorial de mysql dice:
The MyISAM and (as of MySQL 4.0.14) InnoDB storage engines also support indexing on BLOB and TEXT columns. When indexing a BLOB or TEXT column, you must specify a prefix length for the index. For example:
CREATE TABLE test (blob_col BLOB, INDEX(blob_col(10)));
completo en:
http://dev.mysql.com/doc/mysql/en/create-table.html
ya que lo arregles te marcara el siguiente error:
1071 : Specified key was too long. Max key length is 500
y ahi, bueno, hasta ahi llego, suerte.