Error message

• Warning: Cannot modify header information - headers already sent by (output started at /home/cultuur/domains/cultuurspoor.nl/public_html/includes/common.inc:2525) in drupal_send_headers() (line 1038 of /home/cultuur/domains/cultuurspoor.nl/public_html/includes/bootstrap.inc).
• PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database: INSERT INTO {watchdog} (uid, type, message, variables, severity, link, location, referer, hostname, timestamp) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?); Array ( [0] => 0 [1] => cron [2] => Attempting to re-run cron while it is already running. [3] => a:0:{} [4] => 4 [5] => [6] => http://www.cultuurspoor.nl/user [7] => [8] => 38.107.179.224 [9] => 1337526397 ) in dblog_watchdog() (line 155 of /home/cultuur/domains/cultuurspoor.nl/public_html/modules/dblog/dblog.module).